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.
Tipping incentivizes servers to care about getting more tips. This is why there is a stereotype of American servers rushing you out of your table to seat the next party, upselling on more drinks/food, and constantly interrupting the setting by "checking on" the party.
A good waiter gets the main plates on the table after appetizers are finished and responds when I flag them. They are a queuing manager that synchronize orders to the kitchen to optimize delivery to the table. Tipping does not inherently incentivize this, and I'd say it actually incentivizes the worse service in the form of clearing the table as fast as possible in order to acquire the next table's round of tips, or as is often the case, crowding a table up with every appetizer, side dish, entree, and drink the table wanted throughout the dinner.
I find tipping makes many customers treat "servers" like faceless servants, making them feel like prostitutes forcing fake smiles and gritted teeth at bad behaviour.
In a non-tipping culture you learn to treat waiting staff as more human. Arseholes get kicked out, not "smiled" at.
The last German restaurant I went, I was in a party of five. Four of us got our orders somewhat promptly while the fifth waited nearly half an hour… for a frankfurter. Between that and the trains I got this sense that German efficiency was overrated.
One bartender I talked to made the (astute) observation that people feel more generosity toward individuals than to restaurants -- it de-personalized the transaction from the customer perspective, which turned the service charge into a food tax.
In other words, someone's being dishonest.
In most cases, still, the model I seem to see (and I live in the PNW) was a 15/18/20 tip model, and for personal services (nails, hair, etc.) 25.
Food servers would have us believe that poor tipping and other practices have them one shift away from being homeless, or "I have to pay the IRS to serve you, because they assume I'm getting tips I'm not"...
... and yet, when a 20% "tip"/surcharge (which would be on the high end, I feel, most of the time) is added on to every order...
"This sucks, we're making less money".
Very few restaurants would pay an hourly wage that is equivalent to what waiters are getting tipped now. So the waiter will just get less. Just look at what non-tipped restaurant workers get paid, not well.