There are a few reasons:
* Anyone can write code now, so code itself has lost some of its value
* Maintainers can write code without contributors' help
* The quality of AI-generated PRs is now high. We can't call them "slop". But they scan the repo, find nitpicks, and create PRs. The important thing now is not quality, but attitude
* In the first place, I think contributions just for the sake of "contributing" are unhelpful
* Having commits in a well-known OSS project on your GitHub profile can give you an unfair hiring advantage. We don't like contributions made mainly to get hired
* I don't want to see a lot of wasteful PR every morning