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).
Yep, from what I’ve seen the base model is actually great value, especially for an Apple product. But that value disappears very quickly if you want to boost any of the specs, because they still massively overcharge for upgrades.