Bingo. When presented with a buffet, people (myself included) usually have a fear of "missing out" the good stuff, so they just load a little bit of everything to their plate. At a buffet, you usually don't have the information about (1) how filling an individual ingredient is and (2) how well they go together. So each and every time, you end up with too much food which doesn't really combine. In the end, you leave too full and slightly unsatisfied. On a menu, the individual menus or plates have been tested for months against the cooks and guests, and the kitchen has adjusted plates which were always returned with leftovers to be smaller and/or removed meals that led to too much complaints
So basically, on a buffet you will get an untested meal designed by someone usually not competent enough to design it (you), every time.