Not only does Metal use Swift bindings alongside Objective-C, as per John McCall's own words, that is the plan and to fix where that might still not be the case.

Embedded Swift project also started as means to replace Safe C use cases at Apple, like iBoot firmware.

https://support.apple.com/en-jo/guide/security/sec30d8d9ec1/...

https://github.com/swiftlang/swift-evolution/blob/main/visio...

Once upon a time, C compilers were quite lousy versus handwritten 8 and 16 bit Assembly code.