Because Windows doesn’t support OS-wide text formatting/manipulation like macOS does.
The system already existed in macOS so it was easy enough to plug writing tools into it, but to do the same in Windows would mean completely rewriting how Windows handles text display and editing (and no doubt causing an avalanche of compatibility issues with old apps).
Seems very unlikely this is a rights expiry issue, so I would imagine they’re clearing out to make way for new ports at some point next year.