Throughput, expectation of service and number of tables/waiter are very different for coffeeshop/casual diner and place that sells $60 steak. In casual restaurant you can expect one waiter per 8 tables compared to 4 tables/waiter in fine dining place. People easily take 2x time to eat the same amount of food in fine dining place compared to something cheaper. In fine dining place waiters are better trained/educated (ever tried to ask for wine recommendation at Denny's?) and dress nicer.
Higher tips per person are totally expected in fine dining place purely from economic perspective.