That's a very simplistic view of what Microsoft offers. They don't sell an office software package but a very robust solution for running the software side of a business.

The OS, office package, email (server and client), calendar, cloud & backup, BI, etc. all aligned work almost seamlessly with each other (compared to the alternatives for sure).

Nothing on the market comes close and that is the reason they are worth trillions, not because they use closed formats.