I think there is also another problem here sometimes: people who don't really go out for meals but when they do, feel all important and use it as an opportunity to exercise their 'customer is always right' mandate and simply throw their weight around by ordering awkward combinations and things that aren't on the menu. When you combine that with bog standard fussiness it becomes a teeth grindingly awful experience altogether.
It's not self importance but insecurity.
I remember seeing a documentary which featured a restaurant in Hollywood USA ( 'Spago' I think) where the narrator pointed out that most actors are notoriously insecure and that most 'A-list' actors will never order something from the menu at Spago, because this would mark them out as ordinary: they have to have a special dish that the chef prepares only for them.
This was beautifully lampooned by Danny de Vito in the 'Get Shorty' film: he meets John Travolta and Rene Russo (+ possibly one more person) at a restaurant, hands back the menu unread and orders an egg-white omelette with chives for everybody (and which nobody actually eats.)