I certainly wouldn’t want to have to find/remember/click through a state listing to find each college I want to read about when I can just find them in an alphabetical list.
Yes, there are 1,200 + institutions in the US (just those reporting SAT scores to IPEDS - there are probably many more). IME, CC focuses on those that have the most interest. It doesn’t profess to be a comprehensive database of every school in the country. If there is a school with substantial traffic/discussion/requests, I’m sure it would be added.
Not long ago, there was an entire section with dozens of schools that averaged about a post per year. It was rationalized to the schools that showed interest, just as most online social media sites focus on those that engage the audience. So CC will adjust with the audience demand.
The existing state forums are the largest states with the largest populations, largest state university systems, and most interest from forum members.