From the article, "its productivity software is used by hundreds of millions of corporate users, a captive audience to whom it can easily promote new AI products."

Their end users are what they ultimately sell. They are captive audiences. This is what monopolies/platforms do. It's never been part of MSFT's DNA to care that much about end user experience. Who they really cater to are the IT decision makers, etc. These people can then show some numbers about "AI adoption" and "productivity" gains on their Power Point slides presented to their bosses. MSFT's value is delivering that to them.