Why does everyone have a tip jar?

I can understand tipping a waitress or waiter, and even maybe the pizza guy, but why should i tip dairy queen workers or gas station attendants or starbucks workers, im already giving them my buisiness, plus they dont need the tips like a waitress does, i should start asking for a tip for fueling their company with my buisiness, jk. But really why does everyone want a tip all of a sudden for doing their job, i do my job everyday, i actually help people and go out of my way for others and i would never even think of asking for a tip for doing my job, i understand times are hard everywhere but the tipper could use the same excuse and i know im not forced to tip its just the fact that everyone wants a tip for doing what they get paid to do. What do you think, am i being a prick or is the tip jar showing up in rediculus places these days