What group do I want to be a part of?
The group of professionals who do their jobs well, are recognized for doing it well, get referrals from their clients resulting in new clients, and who get tips and drinks while working!
That's what I'm sayin'.
I've only been tipped once, and that was as a second shooter (the couple had separate envelopes for both the primary and myself, which they handed to each of us). However, I've only been shooting weddings for about a year, and my primary was thankful for it, but not surprised. It seems to be much more common with asian couples/weddings.
I have received tips as an event photographer. I have never received a tip as an architectural photographer, my main source of business.
Tipping is seen as a reward for personal service. Not a bad thing. Commercial photography is viewed as a business transaction between two professional parties. There is less emotionalism in the transaction and the contracted price is often higher (we hope).
What some are saying here is that by receiving a tip one is perceived as belonging to the lesser paid personal service group and not the more respected personal service group. This implies that you are not a peer of the client but rather belonging to the servant class (that, in theory, does not exist).
Frankly, I wish everyone was able to be paid more so tips would go out of fashion.