Having spent a bit of time as a boat monkey and as a paying diver, I junderstand both sides of the argument pretty well. I think that it is best to watch people set up their gear, you can learn a lot about the way they will dive. I am standing there and can help if I need to, and earn some tips as I do it. I will say that I would never set up another person's gear unless they tell me to, and even then I will wait until they can watch me do it, if possible.
As has been mentioned before, DMs get paid subsistance wages in a lot of places, and every extra buck counts. All we want to do is have the money for a few beers after work. Is that so bad?
Also, keep in mind the number of new and/or inexperienced divers that show up at a lot of resorts. They way they dive can make even the nicest person jaded in a couple of weeks, and they will simply assume that everyone is going to dive as if it is their first time. Its easier that way.