Three fact that it's not a product anymore doesn't mean it's unused; a quick search says they at a minimum used it in 2021: https://www.microsoft.com/en-us/microsoft-365/blog/2021/07/0...

Microsoft uses Clippy for the paperclip emoji in the Fluent Emoji set. The trademark is why the open source version of Fluent Emoji doesn't use Clippy's likeness.