First world problem isn't a problem. Why is OP getting all pissy over someone wanting tip? Say no with a smile and go on your way.
yeah i delivered pizzas for years.. and there were times i said exactly that- "how much change you want back?". mainly because its just easier to ask then wait for the customer to think about telling you. 90% of the time, theyre like "oh yeah, just give me $3 back". and thats that. 10% of the time they are assholes like the op and say "ALL OF IT" and call the store saying you demanded a tip.
so the few ruins it for everyone, and you go back to just handing back all of the change without saying anything, as if thats normal procedure. the problem is, you would be surprised how many people either forget to give you a tip or they just dont know theyre supposed to *behind the door i hear "GET THE PIZZA KIDS, MONEY IS ON THE COUNTER AND MAKE SURE YOU GET CHANGE"*
the point is, you should know if you need to leave a tip or not before you go wherever it is. if you dont know, dont be surprised if someone acts like they deserve one. of course they make an hourly wage- that has nothing to do with the fact that its posted on the fucking menu to tip the drivers.