Lets put some numbers here. An episode of Enterprise costs about $1.5m. Between distribution costs, and profits for everyone you probably need at least $3m in revenue/episode. By the end, Enterprise was only getting 3m viewers. Apple just set a rental price/episode of $1. Do you think you can get every viewer to agree to pay for what they were watching for free?
I'd be willing to pay $1/episode, and I'm sure a lot of people on this board would too. But until the nature of the TV market changes dramatically, you're just not going to get 3+ million people to agree to pay for each show.