I'm guessing because it's a super hacky implementation versus a full and complete one, in addition to them paywalling it behind their bullshit M365 subscription.
this would make a lot of sense to me. the windows/office365 code base has got to look so scary on the inside. i can’t think of any other reason why windows still has two different settings applications, with the newer one sometimes opening the older one. i also can’t imagine why teams/other office apps open popups (eg when joining meetings) that prompt you to sign in when you’re already signed in.