I personally see two major factors :

• it's yet another way to collect data for monetization (selling to governments and advertisers).
• it's a symptom of market culture : it exists not to serve the user, but to be a product to sell to the user. In that light, it behaves and evolves exactly as any other thingy which tries to reinvent itself year after year, to keep customers interested, regardless of its intrinsic value as an operating system.

but that's just me, I can't claim to understand the inner workings of Microsoft