Windows as a software package would have never been affordable to individuals or local-level orgs in countries like India and Bangladesh (especially in the 2000’s) that are now powerhouses of IT. Same for many SE Asian, Eastern European, African and LatinoAmerican countries as well.
Had the OS been too difficult to pirate, educators and local institutions in these countries would have certainly shifted to Linux and the like. The fact that Windows could be pirated easily is the main factor that led to its ubiquity and allowed it to become a household name. Its rapid popularity in the '00s and early ‘10s cemented its status as the PC operating system. It is probably the same for Microsoft Office as well (it is still a part of many schools’ standard curricula).
The fact that Windows still remains pirateable to this day is perhaps intentional on Microsoft’s part.
That’s very common with Microsoft products too. Their vendors get to use @microsoft.com emails (distinguishable by an extra “v”) so they frequently pose as “auditors” to pressure businesses into buying licenses.
It’s a grey area because a business with all licenses in order would not care either way, but software being what it is it’s hard to stay compliant all the time even if you try, and that’s when the vultures descend.
For example say you appoint a new CTO and they realize your company of 200 PCs uses pirate Office copies, so they buy 200 genuine licenses, but they’re cut short of actually installing the matching Office version because Office is a piece of malware-acting crap and is actually very hard to completely purge from a domain install. So they end up holding correct licenses but using technically pirated versions. This is where a genuine audit would not care (you paid for the newer version and are using the older, crappier version; due to their fault, I might add? you do you Microsoft got paid) — but an unscrupulous vendor would try to scare you into paying more to “fix it”.