[…] not speaking about the dive industry here, I've been to many places in Europe, places where tipping is not part of the culture, where the service has been downright rude, IMHO. Maybe it's cultural expectations, I don't know. But does that mean I have to tip in order to "buy" civility, a look in the eye, and something other than a scowl? Maybe it's just that I walked like a tourist, looked like a tourist, and quacked like a tourist. Being pleasant and respectful to the person serving me (a given) didn't seem to change the equation. By contrast, in SE Asia, service is delivered by polite, humble, smiling people, almost without exception.
I believe you're right, it's all about cultural differences and expectations.
In France, for example, a waiter is basically expected to seat you, take your order, serve your food, and bring your check (you need to explicitely ask for it, or you will wait a looooong time).
Likewise, a taxi driver is expected to drive you from point A to point B.
Putting on a happy face and making small talk is not part of their job requirement.
As a matter of fact, many customers from the upper classes will frown if you try to make small talk while serving them; it's considered unprofessional.
Perhaps that mentality comes from the times when people in the Old Continent had servants who had to work discreetly and make themselves almost invisible.
Or perhaps it's something else. When Disneyland Paris opened years ago, people here were chocked to find out that the employees were required to smile constantly. For many French people, such a demand was unacceptable as they felt people were not smiling robots and that the company infringed upon the employees' basic rights by forcing them to be hypocrits and express a happiness they didn't necessarily feel.
I can easily see why an American in Paris would feel offended by the "coldness" of many professional waiters (not talking about the real obnoxious jerks).
The good thing about France is that tipping is by no means mandatory.
If you don't like your waiter, don't tip him.
If you like him, leave the tip you want and thank him personally.
If he's a total jerk, leave a 1 cent coin just as you're leaving the place… that's an insult !
The one place where I would disagree is the part about tipping in order to "buy" civility. I would never tip someone in order for them to be nice to me.