They weren't around when this whole thing was started. There's also the FCC's involvement. I don't know the exact rules, but I believe the networks are still limited on the number of stations they can own.
See, the government doesn't want someone controlling the media the American public consumes. (Insert your jokes here.)
Anyway, if they cut out the middlemen who would air their content? They'd lose massive market share numbers, and then advertising dollars. Now they don't have money to fund content, and so on.
The system is changing as Netflix has shown us, but it takes time. You're against CBS Access, as am I, but that's basically what you're suggesting Fox do right now.
The weird thing that holds together the old system is local news. Find a fix for that, and you can leverage that into an empire. How do you provide local news/content once the old system is gone?