"That's lock-in, not a technical advantage, as are most of the other things you list."
Call it what you want, there's real practical benefit in being able to have centralised security configuration. Knowing that when you lock out a user account on the domain, that they also can no longer log into every database server and so on has massive practical benefit.
"Well, and there are several enterprise-grade relational databases that don't come from Microsoft and don't come with Microsoft's strings attached: Oracle, DB2, and Spanner for example."
I already mentioned Oracle, and sure, DB2, though it's a small player. Spanner is neither a true RDBMS, nor used widely in the enterprise.
I get it, you hate Microsoft, that's fine. But don't pretend MS SQL server isn't widely used, and it's widely used for good reason - it's a good product.
Besides, even your argument about vendor lock-in makes no sense. SQL server for Linux is open source, the whole point being that it's easy to migrate to.
The reality is most companies would rather pay for something solid and reliable like MS SQL server that integrates well into the rest of their ecosystem, than have something free but shit like MySQL. As I said before, you may have your own reasons not to want MS SQL, or for just hating Microsoft, fine, but don't expect everyone else to agree with you when some of us actually have a wide range of RDBMS experience and aren't just pulling nonsensical theories about a particular product out of our arses as you clearly are.