I'm 29 and I don't do this, but I understand why it happens. I've personally waited in line outside of gay bars, but usually only during pride or Market Days. The massive number of drunk people in a celebratory mood is really fun.
A friend and I once decided to move on to Duke of Perth from The Red Lion. On our journey we walked past several bars with lines of Trixies and Chads shivering in the cold. We walked into Duke of Perth, which was half full and had a grand time.
I assume these other bars were "the place to be." The beautiful people will be there. When I go to the bar, I go to drink, but if you are looking to meet people, I guess you go where the pretty people are.
Now, if you want to know who decides which bars are "the place to be," I can't help you with that. I'm just glad it's not the places I go to.