So, a couple of things:
1. It's not necessarily for discovery of a new ride. In this case, *none* of the rides are new, they're often extremely old, and there are plenty of other ride POVs to watch if you want to see Pirates for example. But a lot of them are terrible and Disney has more than enough professional equipment to make a video that looks really good. In these cases I think people just watch these videos to reminisce, really. I follow a guy who somehow creates very watchable Guardians POVs (along with others) and unfortunately I can't be down there to listen to September as much as I'd like but I can watch this video of it.
2. There are cases with new rides where I don't mind being spoiled, namely to figure out if I could handle the more intense ones. Velocicoaster is a really good example. Haven't gone on it yet, still not sure if I'll do it, but watching it and getting more familiarity with the twists and turns gives me a little more confidence that maybe it'll happen in the future. A lot of these POV channels are more focused on the more intense stuff.
Would say though that in most cases for new rides then yeah, I'd prefer not to be spoiled. Haven't watched anything from EU except for Universal's clip of Stardust Racers, due to my aforementioned issues with rollercoasters.