Why is it easier?

You don’t need to operate on the entire database. You can backup or roll back individual tables and schemas.

You can do it, but if you stuff that process up (e.g. touch the wrong tables/schemas) you’re now dealing with a more complex recovery.

Also are you applying migrations with CREATE OR REPLACE etc? I find that much harder to collaborate on than just standard code.

You only need to migrate if you care about the data and once again that can be different for each schema. And the inverse is true, if you don’t migrate it’s because you’re not preserving data.