The point of abstraction is to limit blast radius of requirement changes.
Someone decides to rename field in API? You don't need to change your database schema and 100500 microservices on top of it. You just change DTO object and keep old name in the other places. May be you'll change old name some day, but you can do it in small steps.
If your layer repeats another layer, why is it a layer in the first place? The point of layer is to introduce abstraction and redirection. There's cost and there's gain.
Every problem can be solved by introducing another layer of indirection. Except the problem of having too many layers of indirection.
The point of abstraction is to limit blast radius of requirement changes.
Someone decides to rename field in API? You don't need to change your database schema and 100500 microservices on top of it. You just change DTO object and keep old name in the other places. May be you'll change old name some day, but you can do it in small steps.
If your layer repeats another layer, why is it a layer in the first place? The point of layer is to introduce abstraction and redirection. There's cost and there's gain.
Every problem can be solved by introducing another layer of indirection. Except the problem of having too many layers of indirection.