Because Microsoft has a document monopoly via their shitty proprietary format that they make sure no competitor can effectively import/edit. And Google is just shitty as usual, but they're a giant free default.

I wonder if with all this antitrust stuff going on we'll ever see regulation in the form of required interoperability and/or data portability? Instead of trying to break up companies, block mergers, etc, I feel like simple technical solutions would be faster and more effective.