Yeah I think if you’re coming from the startup or less so tech in general you may not realize how ubiquitous Microsoft is at work. A massive amount of companies are Microsoft from the ground up. Not to mention there are some entire industries where to run the necessary software you have to use windows at the very least.
Usually companies that don't let their workers choose their tools. They buy what's cheap and looks good on paper.
For companies, there is no sane equivalent to Active Directory. The switch is actually much harder than for home users.