It's a little bit like Linux in the late 90s. Postgres is increasingly being used in financial services, for instance, because it's "good enough" -- many teams

It's a little bit like Linux in the late 90s. Postgres is increasingly being used in financial services, for instance, because it's "good enough" -- many teams really don't need Oracle's or SQL Server's feature-set, and Postgres has enough 'interesting' features of its own. It also lets teams own their DB infrastructure and play around with deployment patterns that'd make little sense on Oracle et al because of cost reasons. It's not that Postgres is "killing" commercial databases, it's just that more and more people are, as you said, noticing that they don't need a commercial database for lots of use cases. And support and consultancy -- and even in-team skills -- for Postgres are often available.