

Microsoft had an almost total stranglehold on Office productivity software for about 3 decades, only their formats really mattered. I think they still have over 3/4 of business & enterprise market share.
Google’s productivity suite is probably in 2nd place in terms of usage today (much more popular than office outside of business) which I believe doesn’t have an external file format, followed by either LibreOffice (via OpenOffice, the originator of ODF) or maybe even the Apple suite.
Essentially the support isn’t super ubiquitous because, especially until recently, the percentage of documents created in that format is quite small compared to the Microsoft formats






Oh, I feel like I’ve gotta let you know the (post 2003/7?) Microsoft formats are technically “open” in that the spec is available for anyone to implement, license free
They saw ODF coming and made sure to kneecap any advantage
#3 is an incredibly recent development. You don’t need to go back even half a decade before everyone was happily gargling Microsoft