Safari lets extensions precompile a list of patterns to block and then it does the actual blocking. The extension never sees your browsing history or network requests.

Sounds a lot like what Chrome is bringing in.

Chrome has a limit on the amount of the items in the list.

Originally, Google wanted to max at 30k items, but after the outry, they increased it to 150k.

For comparison, my uBlock has currently 101k of net filters and 49k cosmetic filters.

Safari also has a limit, and it's low enough that plugin developers have had to split their work into multiple parallel plugins or even into standalone macOS applications.

I guess because Safari is relatively unimportant in terms of market share. Not totally unimportant, but not quite the same league.

Probably because of lack of usage of Safari. It was covered in some circles: https://adguard.com/en/blog/safari-adblock-extensions.html