Customers are more assertive and 'fussy' in general; the days of diners accepting poor quality, over/undercooked food has passed. Restaurants don't want bad reviews on Tripadvisor (or whatever) so will pander to their clients. My cousin owns a fairly high end restaurant and big problem for him is customers sending back food that is of perfect standard. He has noticed a change over the years. He said a customer might ask for a medium cooked steak and then argue that the steak is not what he/she expected - that piece of meat goes in the bin and the profit margin in the bin with the steak..