Q4women: specifically women who have ever worked in a bar/cafe setting, do you let people drink for free, often?

So, I was just wondering if this is a thing or if it just happens all the time. I order diet sodas, maybe a beer, maybe a coffee --- nothing too crazy. And after the first time or two, the girl just starts letting me drink there for free (I don't drink much --- one, maybe two drinks tops --- before I split).

Is this common? Or should I take it as a signal? Or is it just another one of those 'nothing definitive can be known cause NAWALT' situations?

I've only acted on the 'is she into me' vibe once, and that was with a whole host of other signals (she was). But I'm just wondering about this, generally. I had thought up until recently it was pretty common and not a big deal.

edit: to be clear this happens at bars and at cafes