Back in the days when I was single, I would prefer going to bars alone.
I could hang out with friends I met there if I wanted to, or I could leave and go somewhere else without having to wait for someone.
Also, going by yourself allows you to move away from one group and go talk to another group or single person without having to go into great explanation why and who for how long, etc.
Plus, part of the reason of going to a bar alone was so that I might not have to go home alone, if you get the drift.
It makes it a whole lot easier to quietly leave with someone if you don’t have to worry about how other people are going to get home, or if you need to get your jacket out of the car etc.