We’re don’t know so it’s impossible to judge without additional information. If it was a cheap marg bar and they cost $5 each, a $10 tip is generous and helps offset possible minor inconvenience. If it was a place where one boutique margarita costs $22, then that’s just stealing and being an asshole customer, especially if it comes out of the bartender’s wages and gets them in trouble and possibly fired. Hopefully the truth is closer to the first case!