You have to add a lot of scaffolding to postgres to make it semi-immutable. datomic just is, wanna know previous user email, just go back and see. Out of the box, without thinking about it.
Immutability is certainly tempting for certain kinds of data. Does it handle use-cases where data needs to be deleted though? i.e., privacy compliance.
Temporality in general becomes super handy if you have something like reports that need to be consistent across time. Or if you want to ask questions about the past. Or questions about the future without affecting the present.
