If one's sole driving concern is making money, a whole lot of evil becomes possible. The other side of profit is power - those with more capital become more powerful. That's the reason Microsoft made this decision. They don't want the average person being able to easily make a local account, they'd much rather force everyone to register an account with them in order to even use their computer. It's just one further notch down the slippery slope of the end of private ownership and personal rights. A small notch, certainly. But it's a small notch in their overall endgame of putting general-purpose computing "back in the bottle" so to speak.

Certain powers in this world want there to be less regulation for the moneymakers in this world. Centralized wealth has been a cancer on humanity for millennia, and we're nowhere near putting the proper amount of shackles on capitalism.