I know that it’s best practice to install contracts at a module boundary, but are there some good uses for define/contract?

I find the documentation aspect of define/contractto be nice. I have some files where the functions are rarely called from w/in the module, and I use define/contract for them.

What is the rationale for installing contracts at the module boundary - simply efficiency?

In my understanding, contracts at the module boundary make it easier to track blame when a contract is violated.