Despite their posturing, how can we trust Microsoft (and other companies like it) ? Windows is a black box. How do we know that there are no backdoors/spying routines to please some governments ? How can we trust that it behaves ethically with all the data it collects ? We only have their word for it.
Well, you often have no other choice. You can go out of your way and install an open source OS, but then there might still be a backdoor in your hardware. Ultimatively, this can not be solved technically, but socially. In a country with a strong rule of law and democracy, you should be able to trust that the state builds no backdoors into your devices when they say they don't. And you should be able to trust the manu…
But, at least, not in the software. That's a large part of the attack surface that just isn't there.