my sister worked in the cable business and explained it to me once:
if you could purchase individual channels, it would cost the consumer a fortune. something less popular can only get in on the coat-tails of something more popular. you get good deals on channels because they are bundled together, essentially. You have to get something you don't watch, so that someone else can get that for less than a PS+ subscription, for instance. This is similar to the way that some internet tv "channels" such as alternative news sites and other premium content providers who produce their own content and use their own bandwidth, function. For just one "channel" or provider, you can pay $50 annually. Now, think of what that would be like if you had hundreds of channels? This way, you at least get exposed to tons of content, albeit 99% useless. Ala carte would force you to always know what you want and then order it, possibly changing your cable package very frequently.
I agree that it sucks, but it's what we're faced with...
If this really comes to a "head", then I don't t hink we'll see true a la carte, but rather, everything as on-demand, as traditional "channels" all but go extinct. CNN can't even get Dish to carry them due to low viewership... (as alternative news website traffic sky-rockets)