yes, they flirt for tips! They don't get much of an hourly wage, and they will do everything short of sex to get that money. I know quite a few waitresses who do it, and i've done it myself.
It's not only waitresses, it's strippers male/female, etc., it just looks more "fake" when a guy does it versus a female.
Unfortunately, most guy's egos overcome reality, and when you're coming off the shift, there they are standing in the parking lot. Some guys got really pissed of when we have to explain to them, "it's just my job"... I've seen quite a few waitresses get called a "wh%$#re" or "****" because they "flirted" for money/tips.
I've also had this happen even in the medical field. It's "drummed in our heads" about customer service. Unfortunately, even smiling can be taken as "flirting" in some cases.
Smiling is something that is well-practiced, as well as our "Laugh" - i kid you not. The last facility i worked in CA, we had to do a "Laugh Class".. If we didn't "Laugh" well enough to pass the exam, it had to be repeated.
I agree with someone else who posted. Just see how the waitress interacts with other customers. If she acts the same with all of the males? She's just working hard for her money.