Part of the reason there's less pressure to change it than you might imagine is that we now have a hundred years of cultural inertia working on, yes, the customers and restaurants, but also on the waitstaff labor pool. At this point, the Americans who seek work as waiters are generally the ones who feel they work with the system and even turn it to their advantage. It's far from all, of course, but the "best" servers at most restaurants probably feel like they're going to make more working the customers than negotiating with their bosses.
So, you've got restaurants keeping their list-prices low and a built-in workforce motivator, customers who expect friendly service and accept that they're culturally responsible for the staff's pay, and servers who stay at the job because they feel like they'll make more than the restaurant would be willing to pay as a "fair" wage (and they're probably right). Now, it's full-on bizarre that we have taken an entry level service job and made it an exercise in theatrical entrepreneurship, and it says some unsettling things about the underlying social order in the US, but I'm not sure that at the nuts-and-bolts level, it's as broken as the people like to imagine.