I can answer that Okie!
Not only does he thank me, but he sometimes drops to one knee and refers to me as "Queen of the Universe." Of course, that's usually on allowance day......
I get your point and have hopefully taught my son that you thank people when they serve you by leaving a tip. I thank someone who opens a door for me. He thanks me for cooking dinner every night (although sometimes his empty plate really says the thanks better).
Thanking someone should have nothing to do with whether or not something is "their job" or not. I thank my dentist after he pulls my tooth....go figure??