Validation often requires examine a model beyond "is this an int?". That model needs to be self-consistent. That requires atomic movements from consistent state

Validation often requires examine a model beyond "is this an int?". That model needs to be self-consistent. That requires atomic movements from consistent state to consistent state. You can do that yourself. Or let the database do it. For things where you can't express it in a database schema, sure. But you'd be surprised how far it gets you.