Science and history programming is sadly low brow. Netflix had a 12 part series of lectures from Neil deGrasse Tyson that were refreshingly thorough and weren't watered down. They didn't seem to have it licensed for very long as I think it's already removed from their library.
Regarding stuff that seems to be geared towards 8th graders, that's just what some people want to see and you couldn't force them to watch anything with more substance if you wanted to. Not everyone has to enjoy the finer things. I don't think it's that they don't know there's a difference. It's just boring as all hell to most people.
If you are referring to Cosmos I just double-checked and it is still on there. I only watched the first four episodes so I would have been really disappointed if they had already been removed.
I think a lot of people like the parent assume that there are large amounts of people like themselves that would pay for a dedicated of niche content. I really don't think that is true. As every indie filmmaker and SaaS entrepreneur knows: the number if people that say they would pay is a magnitude more that the people that actually do.
A lot of industry observers are speculating that a la carte cable would be the doom of a large portion of the smaller niche channels that are bundled by the content companies (like Discovery Networks) with their more popular channels when they sell them to the cable companies.
It was actually named something bland like "Neil deGrasse Tyson Lectures." I doubt that was the exact name but something along those lines. Definitely wasn't Cosmos, though.
Regarding stuff that seems to be geared towards 8th graders, that's just what some people want to see and you couldn't force them to watch anything with more substance if you wanted to. Not everyone has to enjoy the finer things. I don't think it's that they don't know there's a difference. It's just boring as all hell to most people.