Why Apple allow people share Passkeys?

I recently learned https://developer.apple.com/videos/play/wwdc2022/10092/?time=382 and don't understand why Apple thinks allowing share Passkeys would be a good feature.

I feel this is a really bad practice that we allow them to share Passkeys. Is there possible the website could forbid them from sharing it?

Why Apple allow people share Passkeys?
 
 
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