They do stuff like this not because they want to kill the web, but because Apple will always do what it thinks is in the best interests of the company and its customers.
(Who comes first seems to depend on what the technology in question is.)
In the case of WebKit, it's clear they see these "privacy-enhancing" features as a benefit to both, and so they go all-in.
Like removing the floppy drives. Lots of people had good use cases for them but they believed it was the best move for everyone in the long term.
