The Enterprise's holodeck is not for sex. The same safteys that stop people from being damaged, probably keep everything pg 13. Dozens of people can use the deck at the same time, living out completely different fantasies. Each illusionary world only stretches out and on for a few feet, if necessary, so that so many people can co-exist on the same deck. Basic Federation holodeck characters probably do not have genitals. Someone with a background in tech, can tape genitals onto anything. You cant have a pervert fluffing an Andorian harem, three feet away from a child playing baseball, because that kid may slip on his splooge... And sound travels.
Quark's holo suites were only for sex, until the Federation showed up.