I think there are two reasons so many reviewers resort to ridiculously impractical displays of strength instead of giving more practical feedback/advice:
1. It's more visually engaging for the casual knife user. Think of someone who doesn't really know what separates a great knife from a crappy knife. It's very easy for them to see someone bashing it through the hood of a car and to think, "oh that's so badass, check that out!!" and share it with their friends. Hence more viewers, more money for the reviewer.
2. The fine nuances of what makes one knife "better" that another are really hard to appreciate without touching/using the knife yourself. I think there are three things that make a knife great: ergonomics, fit & finish, and cutting performance due to grind geometry matching steel type. None of these things are particularly easy or fun to explain via video. So nobody does unfortunately.