Any who have visited Kassidor, even briefly on business, cannot help but notice the difference in sexual mores between this society and the remainder of human space. Any who have seen a video from there, read a novel or even seen the average photo can't help but notice the difference. This difference is, if anything, LESS pronounced in the Elven Highlands than in many other basins. In dozens of basins women do not wear tops even on formal business occasions, and in the city of Darceen, where the temperature averages above 130F (54C) there is no clothing industry at all. There is nowhere to buy clothes or even buy the materials to make clothing. In many basins it is not considered abnormal to have sex over the rail of a public walkway or on the beach. In many parts of many basins, public sex is a spectator sport with cheering fans.
Since the tubes do not connect to any lands but the Highlands, Gengee and New Midlands at this time, most visitors from Centorin have not seen that. They have seen the relatively formal and affluent culture of the Highlands, where a snug and thin t-shirt, long enough to cover at least most of the cheeks and nipples, is considered proper business attire. They have seen that there is no such thing as bathing attire on any of the beautiful but crowded beaches that rim much of the lakes in the Yakhan megalopolis. They have seen that caressing a woman's curves is considered a polite greeting, and that being in the presence of the opposite sex without at least some body contact is considered a definite insult. Any who have visited Kassidor City for any length of time know that few relationships are strictly monogamous and the average dinner invitation is understood to include group sex.
There are many factors that have contributed to this wild divergence of social norms. Early in human evolution, before they diverged from Chimpanzees, they were thought to be more promiscuous and mated with any member of the troop they pleased. The alpha male likely had the first pick, but no female mated only with the alpha male. This is believed to be the norm for primates when the population is not under stress. So few primates exist in the wild today that we have to use the data from 20th and 21st century texts on this point. When human ancestors came down from the trees, while they were still called 'something-a-pithacus,' it is believed that the monogamous pair bonding system developed. There is some evidence that it may not have been as strong as it is now when humans were picked up and brought to Kassidor. This is because many primitive hunter-gather tribes on Earth were more promiscuous than the Christian Europeans like Magellan who studied them during their age of exploration. It is likely that whatever entity took humans from Earth, they seem to have taken isolated bands who may not have been as rigidly monogamous as the norm even for that time. This all indicates that the humans brought to Kassidor were probably less monogamous when they arrived.
None of Earth's major STD's was introduced to Kassidor. Those taken were probably small bands who happened to be free of them. On Earth, the human body was a integral part of local biology and any opportunistic microbe could make a home there. On Kinunde any microbe is consumed because the planet supports no plant life higher than lichens and no animal life higher than insects. On Kassidor human biology is as foreign as plastic to the local microbes, and well defended to boot. Before any dangerous human diseases evolved, humans could fight it technically. Today the science to build a virus to attack one and exactly one species of microbe or other virus, in the specific cells indicated, is automated. Dangerous STD's have never been a problem and are now completely non-existent. As a first order approximation, there are no longer condoms on the planet. Just about everyone's bodily fluids are safe, whether they want them to be or not.
Probably the most important reason for this difference is direct and deliberate manipulation of the human genome. When the Kassikan was founded, the wizards who founded it had already figured out that at it's root, it was the competition for progeny that was driving the violence that had consumed their old civilization. They understood that the real cure is to stop the quest for progeny by curing aging. They also understood that none of them possessed that knowledge, they had simply bought it during the Energy Age. But they did figure out, very early, how to trigger the same 'seek as many partners as possible' instinct that operates in the hindbrain of the human male. They did that to remove the alpha male system, thinking that while they figure out how to cure aging, they would at least eliminate the next step up the causation ladder. They understood at the time that the price they would have to pay is a population having a lot more sex.
The next reason, and almost as important, is that people having been using advanced biological science to make themselves as attractive as possible since well before the Earth year first ended in 'ad.' No one would choose to be ugly today, it is too much of a social handicap. That does not mean that all Kassidorians are strikingly beautiful, but almost none are fat, bow-legged or puny-punted either. Usually people spend enough on their appearance to get as much casual sex as they want. The average Kassidorian's ability to make his/her appearance what they want it to be is better than a Centorin's ability to make a video image of what they want it to be.
The latest reason for the increased promiscuity in Kassidorian society has to do with a virus that was released in the early 42nd century, around 51ad, from one of Brancetrabble's laboratories in the Trenst basin. This implements a system whereby damaged genes that may have built up in your cells are replaced with good copies from any of your sex partners. This basically makes eternal youth free and contagious as long as you remain promiscuous. It also provides for the drift of genes thru the population, moving as fast as they did during evolution. Or about one thousandth as fast as they move thru the open market. So one keeps up with advancements in genetics for free if one has frequent promiscuous sex partners.
The institution called the Kassikan created the first virus, but not the second. The Kassikan is the same institution that holds Kassidor's portal on the stargate system. The Kassikan is sensitive to the fact that a great deal of the tourist traffic that Kassidor is generating is sexual tourism. This is because the tales are true, and any Centorin male who can afford the trip will find he can spend every sleep with a different pretty woman as long as he desires, and quite often, she'll treat him to dinner. This has caused a serious mismatch in the sexes as far as tourist and immigrant traffic to Kassidor. Those women who have gone as sexual tourists to Kassidor have been at least as pleased as the males, but Centorin has sent a lot less of them. There are meetings happening at the Kassikan where this issue is discussed. There are those who favor releasing the virus that brought promiscuous sexual desire to Kassidor, thruout the remainder of human space. They possess sufficient genetic and viral technology that the decision will be made at the Kassikan and the wishes of the Centorin and Empire governments need not be considered. Their deliberations may take many years and the result will be fact before we know what their decision was.