What's with so many YouTube videos of people just talking with random gameplay in the background?

[R13247]

There are so many videos, about anything and everything, totally unrelated to games, but the uploader will be talking while random gameplay is in the back round, usually some first person shooter or mine craft or something? Like randomly walking around for no reason.

 

[fungi]

https://en.wikipedia.org/wiki/PewDiePie