From what I can tell, a lot of foreign run restaurants in the U.S. seem to try to play this game, and then make up to minimum wage (as required by law). What this inevitably means is less cash for the wait staff with hustle and awareness while the really trashy wait staff that do nothing and have zero awareness end up making the same amount for less work.

When I do restaurants, I (try to) tip well. If I'm alone and a waitress (or even waiter) wants to drop in for a quick chat, see if I need anything, etc. that's a plus. Obviously if we're engrossed in conversation, I don't want to be interrupted mid-conversation, so wait staff who hang back and either wait for a break in conversation or come back to us also get thanks. Paying attention to drink levels, letting us know there's a delay in our food, etc. all are welcome stuff that increases the tip level.

I get not everyone is actually judging their waiters/waitresses, but you can definitely tell the difference between average and bad, and average and good even if you aren't looking.

So the good ones can make a ton from tips..and by making it mandatory you're just robbing that potential anyway.