If you're working with clients that requires you to have security certifications it can be a real pain in the ass to certify your setup for everything vs just using the 365 stack.
It's honestly pretty expensive compared to the alternatives. If you compare a business setup with windows plus office etc plus the support fee you can get all of that for free plus a much lower support fee from a variety of independent companies with Linux and libreoffice.
The typical office worker really doesn't need the few corner cases where MS office maybe has an advantage. Honestly for a business I would even go with Google tools. Same data privacy issues, but at least the product works great. MS office in the cloud is hot garbage.
Yeah but at least Google offers a good search engine while sniffing all your data. Microsoft products are usually hot garbage, sniff your data and then loose it.
Also what is the Amazon index?
I have a government job (shocking to me still) and everything is on Exchange and 365. I don't know why, other than "nobody ever got fired for recommending IBM."