What the Cusian said.
Several companies sell their channels to the cable companies for a fee (say $2 per month per subscriber). The cable company delivers the channel to the subscriber for $2 + the delivery fee + profit. Theoretically, this was how cable evolved. Pay a subscription rate and media companies would be less dependent on advertising. The problem that has happened over the years is that the revenue from subscribers was fantastic and they could charge for advertising, too. It all led to bloat (400 channels and nothing on). For example, ESPN is a highly rated channel, so to increase revenue, they can charge the cable company more to carry it. To further increase revenue, ESPN can either jack up their rate (which they have) or add more channels to their bundle (if a cable company wants to deliver ESPN for $2, they now have to deliver ESPN 2 for $1.75 and ESPN News for a $1) so that bundle cost is more. Other media companies do the same thing and voila, you're paying for 200 channels, and you consistently watch 12 or whatever so you're paying a subscription fee for a bunch of channels you have zero interest in. You can't control how many channels the cable company provides you for your monthly bill because the packages are structured so the typical family almost has to have the full package to keep everyone happy. Additionally, cable companies want to maximize their revenue, so they rent you DVRs for astronomical prices and make it difficult for you to cancel or modify your subscriptions. ESPN in particular is a very expensive bundle that 100% of cable subscribers are pay for but maybe 25% actually watch.
Ideally, you could subscribe to the 12 channels you want, but this is difficult because several media companies own their own suite of oftentimes dissimilar channels and refuse to sell them separately, and it takes a lot of revenue from small media companies and kills innovation (however, vimeo and youtube have become a sort of incubator for media). AMC could never have done something like Breaking Bad or Walking Dead if they didn't have the revenue.
When a household cuts the cable cord, you can pick to some degree what you would like (slingTV for one has a couple of packages, but you're still paying for a bundle of channels - for me, it's great, because I only need ESPN for college basketball season, so I can cancel at the end of March - same with HBO and game of thrones). I think single channel subscriptions aren't viable because the revenue isn't enough. Netflix and Hulu offer some great content as well as being able to timeshift your viewing much like a DVR. Ultimately, after cutting cable, I only pay probably $10 less a month, but I can cancel some packages and netflix or hulu, HBO based on how I feel. We don't watch a ton of TV in the summer, so I put most of the subscriptions on hold. Over the course of the year, I pay less.
