The grandparent described the environment being "exactly" like iOS. That would mean no terminal, for example. It would mean no 3rd party dev tools that can do much of anything (except SSH into another computer and do dev there). No Homebrew. Web development would be impossible - all web devs would leave.

Sounds like a lot of negatives for Apple and few positives. Makes more sense to make it difficult for common users to do the things they don't want them to do.