Several recent family weddings had buffet service, and the food definitely ran out early - to the extent that some guests literally had nothing to eat. Many of the culprits were kids who took way more than they could possibly eat. Their parents either did not notice or more likely, did not care. Young kids, given an unlimited food source, will often take as much as they can physically manage.
My table lost at the "table lottery" and got one of the last places. There was literally no food other than brown, wilted salad to eat. A family at an adjacent table noticed and offered us their kids' uneaten food. Uh, no..... Several people at my table got up and left, saying there was no point in staying. OK, that's a bit rude, but understandable. Especially when they had hungry kids themselves who, I guess, were expected to sit quietly and hungrily and just watch the more fortunate guests enjoying their meals.
I always suggest being conservative and serve an over abundance.