A YouTube Director talks about the evolution of YouTube as channels:
What we’ve been working on for the past two years is what we sometimes call the “channelification” of YouTube. You’re right: In the early days, YouTube was a repository of videos, and people would just search to find the videos they wanted to watch. We’ve made a big shift, and now the entire YouTube experience is oriented around the idea of channels, and there are two reasons that’s important. One is to help users find the content they love and stay engaged with it, regardless of what platform they happen to be on. So if you’re on your PC or laptop, and you subscribe to a channel and then pick up your phone or tablet, that subscription carries through, and it makes it really easy for you to kind of stay connected to that content.
YouTube is online TV; for many, like myself, it along with Netflix replaced my TV since I don’t have cable.
YouTube pages are also a brand’s TV channel. The brand runs original programming on those channels, like TV stations, and can take a piece of the ad-revenue.
It’s also worth noting the emphasis again on content as agnostic across devices. Viewers should be able to simply pick up where they leave off across any device.