There are so many subscription models now. It's too easy to get an adblocker, rendering income from ads non-existent.
I have been giving youTube red a go, just so it stopped interrupting things I was watching with an ever increasing amount of ads.
It's not been bad so far.
The subscription model is taking off everywhere, spotify, iTunes, Adobe, LOTS of internet services; cloud flare for one.
With the likes of Adobe, if, like me you use it daily it kind of makes sense. You always have the cutting edge software, it works great (I've tried, really tried to find an alternative that replaces it at a cheaper price... no joy so far).
I think if you only watch youtube occasionally it's not worth it, if you watch it a lot it's worth the month's free trial at least.