Chain restaurant margins are not razor thin, to give an example, Olive Garden spaghetti costs about 30 cents total per bowl and is sold for $10.
I do not believe at all that the resistance is from customers or wait staff and everything to do with big restaurant chains refusing to pay a living wage, which also goes for kitchen staff who are also generally underpaid. Why pay your staff well if you can put the blame on the customers if they don’t tip?