[The_Colonel]

I think people like this strive for control. Their projects are like their little kingdoms where they have the last say. You might say that they can still retain such total control even in an open source project (OSS doesn't necessarily imply "democracy"), but there's still a possibility of a vim/neovim-like split. Bram was also quite opinionated, which led some developers to fork vim. Bram was very clearly quite unhappy about the split in the community, and keeping sources closed will prevent such a scenario.