That may well be the case, but in the restaurant industry it is potentially keeping in place a local maxima. No restaurant can experiment with spending less on front of house and more on back of house, ingredients, or space. That percentage of revenue (~25%) is locked in and untouchable.

Spending 25% on the front of the house? That's a huge amount - labor is probably less than 25% all in.

20% comes off the top in the form of tips that never make it to the till. The other 5% is a fudge factor for the fact that you still need to pay something in wages.

Your numbers imply that the hourly productivity of a waiter in the US serves food that is just under $50 on the menu and thy make a $12.50 tip on the same. More in areas with a higher tip minimum wage. Do those numbers seem reasonable to you?

I don’t understand where you are getting those numbers.