I agree. But my question is why don't the dive operators just include gratuities in the price? This way the crew never gets stiffed.
Some of us pay our crews wayyy better than others. We appeal to a lot of poor college students because we offer great diving quite affordably. We don't actually
expect tips, but they sure are nice. It gives an idea of how we're doing. When some college kid throws 20 bucks in the tip basket, we understand that he gave what he could afford. When some guy wearing the best of everything who brags about his trips to Indonesia hauling a $7,000 camera rig who is a mediocre diver but won't take suggestion leaves $20, we know his story too.
But to more completely answer your question, Americans want a deal. That's why airlines put bag fees on top of ticket prices. That way they don't have to raise ticket prices, they can raise bag fees and hear the same amount of bitching instead of seeing a drop in ridership because prices are too high. To illustrate this, I used to have a partner. My partner maintained his price structure for his dive trips. I went to all inclusive pricing which I find a better deal. We include beer and wine, nitrox, and we cut 10 passengers off the boat. The majority of our clients remained with the other boat because the base price was cheaper. And because there are a few folks out there that don't like me, but that's another story. Anyway, my boat was more comfortable with 10 fewer folks on it, and was a better deal for folks diving nitrox (it drove more of my guests to use nitrox, and we've never had a case of the bends from a nitrox diver), and was actually less expensive for the client. It almost put me under. We had to move to Florida because we couldn't compete in the Texas market anymore.
That's why dive operators don't include tips in the price.