People are very willing to use new things when something they are using can't do what they want to do.

Dogma is more effective than reliability concerns in my experience. It just happens that the dogma prefers Postgres in this case.

It is just difficult to make these decisions in a more informed way because it requires actual manual testing with the concrete use case and also a decent understanding of databases in question. Chances are you won't have people that understand these things or those people won't have much of a say in decisions.