I personally don't believe people are entitled to watch games on youtube, but at the same time I've been convinced to buy as much as I've been turned away.
I'd also like to note that the people who have been doing these videos the longest and most successfully have their own interesting personalities and show elements that make it work beyond just showing gameplay. Various people will have a preference for various channels, but overall they do a lot more than just sit around and record. Many are funny, many are critical, many do a lot of fun editing to highlight humor or drama.
There are some channels that are essentially video piracy mills that run through the latest games as fast as they can on youtube with no commentary. Publishers will want to go after those first.
The better channels that I watch play old games. There's a well known group that honestly just runs around being silly in half-life 2 gmods and it's hilarious, or play older games in co-op. I find how other people play games fascinating and interesting, so even after I finish some games I wach how others have played them, did this for the Dead Space series and for TLoU.