I have some stories. As a former bouncer, and bar manager I never understood that either. The bartender has to clean up, so she'll be there all night you aren't taking her home unless it's the middle of the night. So why not go after one of the women who is drinking at the bar and can leave at any time. Second, they're usually not single but pretend to be. One of my good friends was engaged but wasn't allowed to tell customers, and she didn't drink. So she'd let guys buy her shots and put water in the shot glass and take it with them, then when I got there, I drank whatever liquor any guys had bought her up to that point. I have another good friend, she actually was single but I remember one year close to Christmas, she was bartending in a 49er jersey that one of her customers had bought her and there were like 7-8 dudes lined up sitting at the bar desperately trying to get her to date them, two even got in a fight over her. I worked with another one and for at least 6 months this guy would come in on every single one of her shifts spending a lot of money thinking he's increasingly getting closer to dating her......meanwhile she's been with my roomate/best friend for years and pretty much lives at our house but this poor guy thinks she's single and that he's got a shot. It's a dirty business.
They're good at lying too. We had a new one and after a month or two we made out after we closed the bar and she told me she was single for a few months at that point. We hooked up that night and in the morning her phone was dead and I didn't have an android charger so she asked if she could use my phone to have her baby daddy/roommate come pick her up. I said hell no and when I dropped her off at that apartment complex, that dude was standing on the lawn staring at me. Weeks later he found me on FB and messaged me talking shit. I said talk to her, she told me she was single. I never heard from him again and she got fired soon after that.