You seem to forget they've scaled back on Muppets as well - this is because most other preschool shows have small casts of usually three or so main characters; it's decided SS has too many characters - both human and Muppets - hence why they've scaled back. We have the "Core Six" of characters, where one or more of each of them is mostly likely to appear in every episode (Big Bird, Oscar, Elmo, Abby, Cookie, and Grover), the others have been reduced to minor/secondary/supporting characters.