It's true, and soon there won't be.
I think you are thinking there will be an objective reckoning of features/performance/reliability and somehow since OSS wins all of those they will choose it, and as far as I am concerned, thats not actually why they choose their database in the first place.
A million b2b apps are developed on sql server because visual studio/microsoft makes that easy for their .net stack, and oracle sells to executives or other manager types and gets shoehorned into projects or set as a requirement before smart people get involved ALL THE TIME.
A lot of it still comes down to enterprise pricing, support, integration, and name recognition.
However, I am thankful my own bosses can count, and went "WHAT" at the last Oracle bill.
So we're actively seeking to move our own stuff from 'Orrible to PG, and to get rid of the vendorware depending on Oracle.
We just got AppDynamics in (ridiculously versatile and useful monitoring). Speaking to the AD sales engineer, he said a lot of their Oracle-using customers are eyeing up PG similarly.