It's not
just that.
In part it's buying yourself a place without waiting.
I know a bartender who runs the entire bar area (the actual bar plus maybe eight four-top tables) at a nearby restaurant during lunch. I can text him at 10:30 and say I'd like a table for 2-4 people at lunch at 11:45, and there will be one waiting for me. He just brings one menu to the table, with our drinks (I'll have water, my wife will have Diet Coke, he already knows this) and we usually spend about ten seconds looking at the menu before we order.
We're both busy professionals, so getting us in and out in thirty minutes matters. And he does.
I'm directly paying the guy who provides service to me for a much higher level of service. I'm sure his manager would like a cut of that, but it's the price they have to pay to retain high-skill servers.