Yet another diner, yet another chair with a completely busted latch on the belt. We resorted to pushing the kid right up against the table to keep him from leaping out. This time I asked (nicely) why all of their highchairs were broken, and the maitre d' (or whatever a maitre d' is called at a diner) explained that people break them all the time by yanking the two pieces of the latch apart to get their kid out. So there you have it: Mystery solved. It's not that the restaurants don't care about the safety of your kid. It's that other parents don't care about the safety of your kid!
Which begs the question: Can't someone design chairs with latches that are less prone to breakage?