Lots of it is, of course, right on. Need a horizontal shot of a generically attractive model lounging by a pool? A generically hot dude on skis? A roasted turkey pooping out stuffing? These are useful images that many designers need on a daily basis.
Other stuff? Well, you just have to wonder what the photogs were thinking. “These shots of fat people playing tiddlywinks are going to make me rich, I tell you! RICH!” This is the kind of stuff psychology classes should focus on, because such people are criz-zazy and delusional and roam the streets unfettered.
Given my work, I don’t have much reason to use stock video, but if I did, I’m happy to see that I would be just as amused/perplexed/terrified.