Because it's (or at least it definitely WAS) true. There are valid use-cases for mongo but for vast majority of things, you're better to start with postgres. A

Because it's (or at least it definitely WAS) true. There are valid use-cases for mongo but for vast majority of things, you're better to start with postgres. And I say that as an early adopter - I really wanted mongo to succeed but it just failed all of my expectations. All of them. BTW: this is post about postgres.