I see a lot of claims that those rooms were considered social areas where Romans would chat together, but I also saw a counterpoint saying that people probably wouldn't want to stay for long in a room that smelt like shit and had other people shitting in it, and would want to leave immediately.
Indeed, this article cites a paper that claims that, supposedly, graffiti in Roman toilets is rarer than you might think, which might support the latter.
https://www.imperiumromanum.pl/en/curiosities/dangers-in-roman-toilets(Edited 11 seconds later.)
Lions play with each other’s balls in order to build trust between dominant males
…humans could learn a thing or two