Anecdotal evidence: I worked in electronics sales for a few years before I got a real job, and I never had any pressure to recommend one brand over another. I always recommended what I felt was the best stuff. The pressure is in selling accessories and insurance plans - this is where the big margins come from.
I don't know if you visit other tech websites besides this one, but Microsoft doesn't exactly has a shining reputation amongst people who work in the technological fields. Slashdot for instance, one of the largest if not most popular tech websites, used Bill-Gates-As-Borg as their official Microsoft logo for over a decade. Microsoft is a hated entity. Microsoft got this reputation by basically raping the competition (think: other technologists) in the 80s and 90s, and there is still a lot of bad blood.
And that's a big deal. If I have a medical or car problem or whatever, I go to my trusted providers and ask them for help/advice. When people want advice about technology, they come to the nerds. Nerds who may have got sand on their face from the Redmond entity, or were influenced by nerds who got sand on their face. I'm largely introverted, and somehow people ask me for tech advice all the time, family and friends and random friends of family. Like it or not, I (as well as most of you) are more influential than a random Joe in the world of Big Tech.
And if I or other nerds say Microsoft's stuff sucks donkey balls and to avoid their crappy new iPhone knockoff, go with the real thing instead... that's huge. Sometimes these nerds work sales, it happens, especially while in college. Then they have even more influence.
I think perhaps Microsoft is starting to learn that you can't market your way out of a PR problem. Hence their greater emphasis on open source and open web technology lately. But who knows.