If anything, that was a failure of imagination on writers' part, somewhat rectified over time and subsequent shows. Even in the core shows (TNG, DS9, VOY), we've seen the holodeck used for recreation, dating, study, simulation, brainstorming, physical training, hand-to-hand combat training, marksmanship training, gaming out scenarios for dangerous missions, extreme sports, engineering, accident investigation, crime scene reconstruction, and a bunch of other things. Still, the show was about boldly going where no one has gone before - not about boldly staying glued to a virtual reality display - so this affected what was or wasn't shown.
Plus, it's not either/or. People went to Risa to have real sex (er, jamaharon) with real people, and lots of (both it and them). This wasn't shown on-screen, just heavily implied, as this is where Roddenberry's vision of liberated humanity clashed with what could be shown on daytime TV. Holo-sex was a thing too, but it was shown to be treated more like pornography today - people do it, don't talk much about it, but if you try to do it too often and/or with facsimile of people you know, everyone gets seriously creeped out.