A few months ago Youtube launched their premium ad free service called youtube red. Youtube red allows you to view all of your favorite youtube content with no ads for a small fee. Not only do you get your normal content without ads you also get all kinds exclusive shows and series that you otherwise would not have access to.
I personally don't mind the ads. Most of them are skipable anyhow. The exclusive content has not been enough to lure me in so far. That being said if you needed another reason Google is giving it to you. They have been sending out emails to those who are subscribed offering them a free Chromecast. This seems to be a win win. Google gets you watching Youtube red content on your TV instead of Prime Time television while you get a nifty little piece of tech.
It is not clear if new subscribers will get to take advantage of this. It is likely meant for those who have been early adopters.