The big problem is Excel. Microsoft will make sure never to give that one up. Browser version isn't enough. I'm sure Apple has their reasons for not financing a full-fledged, compatible version, but if they would it would massively increase market share. I'm guessing it's strategic - e.g. not incurring the wrath of Microsoft or a different non-technical, non-marketshare reason.

The world outside of the SV tech bubble runs on Excel.