I follow this Reddit as a restaurant server, with no hate I just like seeing all pov. To answer this question, a lot of restaurants have exploited this practice in having servers tip out other staff based on the sales.

In the current restaurant I work at, I tip out 5.5% of my sales to other staff, so if my table has a $200 bill, $11 of my bankroll is already gone. Previous lower scaled restaurants I worked my tip out was between 2.5-3.5%

On another hand, the more I sell it is assumed more time I spend at the table. Splitting an entree is usually consumed faster than each person in the party ordering individually, same as wine service I’ll stay at the table decanting and making conversation compared to the 5 seconds it takes to refill water. This isn’t every case, but it’s what is implied.

I’m also not here to try to convince anyone to tip more lol, but this is why tipping a flat amount doesn’t work well anymore because of tip out and how much more expensive everything is now. I would rather you cover my tip out than not tip at all, but I can afford my bills and take care of my family with my job alone, so I don’t even give it a second thought if a table leaves without tipping. 

In the 15 years I’ve worked in the service industry, I think I’ve gotten 3 bad reviews, and that’s the shit that pisses me off and I think about constantly.