For creating requests the GUI of postman is way over the top. HTTP is so simple, why not just write that directly in a literate format you can checkin to a repo? For actually running the requests though I agree a gui is nice. I actually use dot-http as an embedded tool in a browser extension. They're still alternatives, just not in the style you're used to.
So is email. The simplicity of a protocol has nothing to do with the complexity of the workflow that produces it.
> why not just write that directly in a literate format you can checkin to a repo?
Because nothing I work on in Postman is something I need to check in to a repo. I need to test HTTP requests, and I've never worked with a code base that had raw HTTP requests in it.
> They're still alternatives, just not in the style you're used to.
The "style" is different enough that entire use cases become impossible.
Let's say I want to copy HTTP response headers out of a log in JSON format. In Postman, I can paste JSON (and various other key-value formats) into the headers field, and it automatically parses it for me.
There are a hundred little conveniences like that that require a good GUI.