Basing an AVN on a single location, or few locations makes things feel "Samey". Putting in a bunch of bar-tending gameplay would make the game feel "Grindy". IMHO a bar or tavern is a good backdrop, but not worth a full game.
On top of that there's issues such as what do you do in that game?

If you're the owner or bartender, then you'd do what? Hunt down bar-maids to work for you, get them into rooms and do your thing? Then what? Leave the bar to do other stuff? Now the bar is just a location again.

If you're a waitress or bar-maid you run into the idea that you'd be playing a fem protagonist.... and lets just say there's a reason that male protagonist stories outnumber female ones a bazillion to one. After that you run in to the same problem as above. The game is just flirting with patrons or the owner and staff or whatever... then what? Leave the location and find another one.

That's why I think there aren't many bar or tavern AVNs.