The main reason is that Apple has effectively deprecated Objective-C for ios/macos development going forward. It's not going away for probably another decade+,

The main reason is that Apple has effectively deprecated Objective-C for ios/macos development going forward. It's not going away for probably another decade+, but all documentation is now in Swift, new APIs are written with Swift in mind, etc. Think of it this way: in 5-10 years, ObjC will be the python2 of Apple development.