I remember when it was customary to tip for service. You tip your delivery driver, or the server at the restaurant you ate at, or the porter who took your bags to your hotel room for you.
I don't quite remember when it became customary to tip for "I'll have a coffee, please" but I know I rejected the idea then and I reject it now. I have never had the barista at Starbucks or the people at Booster Juice come to my table in a food court and say "Was the food/drink okay? Anything else we could get for you?" as a server does.
-James
Current beast: E550 Coupe (M278)
Previous beasts: AM Vantage, E90 335i (modded + JB4 Map2), E39 M5