To add to that, in many areas and for several decades, gay bars were the only safe places to encounter or rendezvous with new gay people. You didn't openly meet new people at church, the social hall, organized community dances, the workplace, etc. The bar was where you could be yourself and safely chat up somebody else.

In some of ways, the Internet has supplanted bars, but not entirely. Meeting new potentially-compatible people in the physical world still happens quite a lot in gay bars.