Except without the content, the ISPs wouldn't have much of a business. What's the point connecting people to the internet if there's nothing on there to see? It's supposed to be a symbiotic relationship not a robber baron one.

Netflix should be able to just block Comcast until they give in and agree to improve their peering.

I live in the UK though, where we have a competitive broadband market. The above tactic is less effective in the US because Comcast's users don't have anywhere else to go.