The big benefit of MSSQL and Oracle SQL is that your database server is almost completely detached from the operating system the likelihood of a system update changing how your database works is nill. With Postgres and other databases it’s not a given. Ironically on Windows you get to extract quite a bit of that back since Postgress on Windows comes with most of its own libraries, however that’s also part of the problem where you can easily have material differences between running Postgress on Windows and Linux.

I am guessing that you don’t want to validate PostgreSQL on all operating systems, but you could always stick to one using software containers.

Postgres is far more dependent on OS libraries which makes it far less predictable.

Of course you could skip patching the dependencies and ship unsafe software the oracle db way.

Postgres is dependent on a lot of OS level C libraries that can materially change how things work.

This means that there will have to be more testing with Postgres and there will be higher uncertainty between different deployments.

All of these can be mitigated and for many organizations the benefits of Postgres might outweigh these downsides but they do exist.