I watch a few, but more so for the hosts than the gameplay. Like, I'll use the Game Grumps as the easiest example. I can say confidently that nobody watches the Grumps for good gameplay, but because they're funny and oftentimes really bad at whatever they're playing. To paraphrase something from a recent episode where they were talking about linguistics podcasts...
Arin: "I feel like there'd be a lot of pressure for something like that. You're just talking about linguistics, so if you mess up one word, people will give up on listening, like, 'get a load of this guy.'"
Dan: "Yeah, it's almost like two guys doing a Let's Play channel when they suck at video games."