You also get to board first and are served first, so if you have your eye on buying a particular food item it likely won't be sold out.

Speaking of food, the past few food flights I've been on have seen a solid stream of meal purchase (sandwiches or salads) without them appearing to run out. That's 100% anecotdal of course, but at least on recent flights the previous claims of just a few meals boarded for a flight was not the case.