Restaurants in the US are run like a factory assembly line, with every person manning a portion of the line being incentivized to get the table out of the door as fast as possible in order to maximize the amount of scraps they get out of tips. In a fixed system, you might sometimes have to flag down a waiter rather than have your glass endlessly refilled even when you're done drinking, and folks might stop walking by asking (if you're lucky) to take your plates away before you're ready.
If you're a person who travels, count the amount of visible staff at an average German restaurant, and compare that to what you see in the US. It's drastic. Orders of magnitude drastic.
