I'd rather tip the guy sweeping the streets at six in the morning in the rain
no one is stopping you from doing so... in NYC it is custom to tip your building's super at christmas for sorting out your garbage all year, tho i think this may be on the wane...
and Mr Tea, please shut it with "i'd rather just pay 20% more". seriously, it is such a smart-assed english university student in america thing to say... there are plenty of things about england i'd like to change... like, i wish when i bought a mixed drink there it had an adult sized pour of spirits in it...
but, the point is the world is the way it is. if you are in a country where tipping is standard (like the US) and someone performs a service especially for you, TIP. and then afterwards write a letter to the Restaurant Owners Association or something about how you'd gladly pay 20% more...
if you are in the US:
if someone brings you a drink, TIP
if someone brings you food, TIP
if someone shines your shoes, TIP
if someone cuts your hair, TIP
if someone fetches you a taxi, TIP
if someone drives you somewhere in a taxi, TIP
if someone carries your luggage for you, TIP
if someone carries your golf bag, TIP
if someone parks your car for you, TIP
basically, if you are asking another human being to perform a task on a one on one basis directly for your benefit, TIP THEM. i mean, we are talking a couple of dollars here...