Part of that is because their mission statement isn't literally regarded as radical anymore. When Sesame Street launched, and really up through the early 90s, it was radically progressive to have a kid's show that tried to teach kids things, and more specifically targeted inner-city kids by using surroundings they would be familiar with. Most of us grew up with Sesame Street just being on the air normally, and most of us here didn't live through the Senate hearings on public television. It's a minor miracle shows like Sesame Street and Mr Rogers' Neighborhood are regarded as mainstream and boring now.