One of the biggest advantages is that a lot of people in the business are already comfortable with the ecosystem. I know that from the perspective of HN that SSMS, pgAdmin, DBeaver, DB Browser for SQLite, et. al. are mostly isomorphic, but from the perspective of everyone else in the business, these are substantially different things to think about.

Whether the popularity of the MS ecosystem is good or not is a separate problem. If we are solving for "make the business go well and I get paid more", the strategy is usually obvious. We can still advocate for OSS and not-so-many-eggs in the Microsoft basket while we get paid for using these technologies. Again, SQLite is the preferred engine in my tool belt. I don't want to have to manage a hosted sql machine. But, sometimes the problem absolutely insists upon it.

Also, if you are using C#/.NET, integrating with MSSQL is always a little bit easier than the other providers. SQLite (and some others) have lackluster types for things like time. MSSQL has DateTime2 and DateTimeOffset that map exactly into the CLR types.