I don't mean for this to put down the Postman team and their hard work, but I don't understand what its fit is.

If I'm writing an API, I'm testing that thing as I work on it, and the tests describe the spec of the API along with any public-facing documentation. I'm also going to provide a nice interface for testing it manually, because there are plenty of tools for doing so.

At this point, what does my team gain from using a GUI to interact with the API? Is it better documentation, better accessibility to less experienced devs?

I admit I'm naive, I'm probably missing a killer feature. I don't feel like I have an API problem though. They work well, they're tested, easy to use, directory structure/conventions/tests provide good discoverability, docs exist where code falls short, etc.

What cool stuff am I missing?