Anyone know how the game picks which sims visit community lots?

Thank you @Cupid @elelunicy and @logion for your insightful answers! I just learned a bunch I never knew before. It makes much more sense to me why I see certain sims at different lots. I hadn't realized teens hangout at the parks in the evening, but I'm definitely going to be paying closer to attention to the sims visiting community lots I'm on more often now.