Tipping

I totally understand why you tip. The prices are lower than you might expect because the waiters and waitresses only get a limited wage. You are then expected to bolster their wage if they provide an adequate service and you are more likely to return to a restaurant where the service was good leading to more tips in the future and more business for the restaurant. What I don't get is why you tip taxi drivers. Did they get me there faster? Was it a more direct route?

I might also have left a couple of door openers disappointed as I just said thank you. Someone also offered to carry my bag but having lugged it around airports and metro stations I wasn't going to pay someone to take it to the lift for me.