And in Korea you *never* tip. You don't pay to the waiter anyway, but at the cashier. Makes for a "cleaner" customer/business relationship: you pay for what you order, period...
In switzerland it's about the same as in france. We rarely tip and it sure isn't a percentage.
At first glance, I guess it could look like that. But think about it: what if the waiter's salary was a couple dollars above minimum wage, and no tipping was expected. Where would the waiter's salary be coming from then? Well, still from the customer's pockets, right? I mean, paying customers are the only source of income a business has. (Unless it's run by organized crime, but that's another story. 
) So it doesn't matter whether the waiter is getting @2.50/hour plus tips or $8.50/hour with no tips, all their income is still coming from the customer's pocket. In the latter case, the menu prices would be a lot higher: say $12 for an entree, where in the tipping system the menu says $10 but when you add the 20% tip you're still paying $12.
It's not the case that the customer is making up for the waiter's low salary: it's just that the waiter's salary is being tied to job performance. If they wait a lot of tables and keep their customers happy, they'll get more money.
It could indeed be argued that a non-tipping system makes for a "cleaner" customer/business relationship. But one could also argue that a non-tipping system provides little incentive for waiters to perform well. (I think that argument is a little weak myself, since there are the same incentives -- "do well or you're fired" -- as in any other job).
I'm rambling. I guess my point is that a little thought on basic economics should show you that the customer is *always* paying the salary of the employees, whether those salaries are low or high.
Information on tips in the US can be found here:
http://tipping.org/tips/
TipsPage...PageTipsUS.html
I wonder if the reason I mentioned before -- it keeps the apparent menu price down -- might not also be a large part of it as well. Under the tipping system A menu item that "really" costs $12 after tip looks like it costs $10. Which supposedly means that customers will think they're paying less than they really are, and thus eat out more frequently.
Same reason why sales tax is rarely included in listed prices in the U.S., and why items that cost $10 are listed as costing "$9.99". Keep the apparent price down to lessen "sticker shock" and get the customers buying more.
That still doesn't explain the discrepancy between waiter jobs and other service-oriented jobs, though. For that one, I can only come up with the "historican reasons" explanation.
I suppose a restaurant that would give their servers a decent wage and not require customers to tip, might not do so well, due the aforementioned psychological effect... other, "pro-tipping" restaurants will seem cheaper, plus you have a choice in how much you tip. (At least it appears that way, ignoring "standards" like 15% or 20%.) So that kind of "inertia" will make it hard to switch... presuming it's desirable to switch in the first place.
I agree with Robin that the customer pays the salaries in the end. In France, and in Korea too, prices include service [that's where the ++ come from: service, then VAT]. When you tip, in France, the tip doesn't go into the bill, so this is not refundable if you're on expenses. Whereas in the US I guess it's more or less on extra tax on top of the bill, and can be included in biz expenses – esp if it's on a visa card. I think this plays a significant role too.
Or maybe I am just trying to justify my non-tipping...
Likewise with tipping: the restaurant would just need to proclaim in the window and on the menus: "Prices include tax and tip. What you see is what you pay."
Of course, that's just my theory. And store owners aren't stupid: if my theory actually worked, some of them would have tried it by now. The fact that I haven't seen that anywhere in the U.S. means that I'm probably wrong.
Contrast this to the UK where waiters seem to be trained to avoid your eye and often display a hearty disdain for the paying customer. In the UK tipping is usually at the 10% level for good service. I often wonder if Punters, Restaurants and Waiters were to adopt the US model whether we'd get a revolution in UK restaurant experience or whether the US model is a product of American temperament not easily replicated?