The desire for an open source app top-to-bottom or the need to use existing databases or tooling would be a good reason. (However, I do think this question is

The desire for an open source app top-to-bottom or the need to use existing databases or tooling would be a good reason. (However, I do think this question is a bit of a red herring: I don't see any obstacles to pulling in a different database in Pedestal.)