Pretty much nobody's personal info is valuable by itself, but it's EXTREMELY valuable in aggregate, because it lets you target advertisement. Like, so valuable it's on the order of tens of billions.

Indeed, and the entire concept of smarter Siri, chatGPT integration as well as apple's ever-increasing Ad surfaces ... is powered by aggegading more and more usage analytics from users. There are so many that come on by default when you install macOS/iOS.

No, you don't need usage analytics for Siri.

(You need it for music to fulfill your contracts with the artists though.)