I always wonder why some many developers work with Postman (or Postwoman), and so without any automation whatsoever. Example: Requesting some JSON payload and extracting some generated id from it looks like a clumsy point-and-click adventure. With curl, you can use any appropriate program to extract output, say jq:
curl acme.org/my/resource | jq -r '.id'
I see how some project manager doing a presentation of a bleeding-edge feature might profit from Postman, but as a developer?
I guess I don't do enough interesting queries to need a dedicated GUI client. I usually rely on httpie over plain curl or postman. I'd never even heard of insomnia.
For one, the GUI allows you to store your various HTTP actions and replay them, and while you can get that in your shell it takes a bit more work to set it up/present it/reuse it.
I've used it often for ad-hoc requests, where there's authentication/OAuth tokens required, JSON payloads that would be a pain to put into the shell.
Obviously it doesn't negate the need for testing or replace tests, but not every ad-hoc investigation needs to be wrapped in a test.