It's the future of entertainment for a new generation tbh. Kids these days don't look up to your typical celebrities anymore, they're going for the more relatable youtubers/viners/instagrammers. It's not that impactful right now, but boy oh boy things will change in the next decade or so.
Social media stars is something that these kids see is possible to become, so a lot of them have social media accounts. It's fair money because if advertisers are getting eyeballs on their products through these videos, then they deserve the money that they get.
The ability to appeal to a multitude of people, editing skills, entertainment skills and entrepreneurial skills are needed to be a successful youtubers. It's simply not turning on a camera and talking. In order to make the big money, then you have to be somewhat skillful in that area. If it were easy, then all of us would be youtube stars.