It’s a service charge and not a gratuity. We add it so that we may decide how it’s distributed. A large party may require several servers and as the owner, I have no control over the gratuities. With a large party and several servers, I cannot even say who the gratuity belongs to. With a service charge however, I can decide that say, 10% is split among the wait assistants and the rest evenly among the waiters. Imagine the mess of having a bunch of tired waiters arguing over who served more desserts or the price of the wines chosen by “their” guests. So, in the interest of our big fat happy family, I call it a service charge and distribute in the manner I deem fair.
PosterChild: a large party can be very difficult to control, some do it well, some just get run ragged. It’s very possible that a waiter who cannot control a party (and that must be finessed so as not to offend them) will be unable to even get a unified drink order from a large table, thus he/she just runs from the table to the bar, to the table to the bar, to the table to the bar… Hours, maybe days later a drunk and famished guest will ask if they might please order food now (yeah, progress) sure enough the third person in the party will say that they haven’t looked at the menu yet, but could they have another Chardonnay? Table to the bar, to the table to the bar, to the table to the bar…