Some time ago I learned that Postman Labs that produces a nice but not-a-rocket-science HTTP client raised $433M at multi-billion valuation and has 500 employees. Isn't it astonishing?
Centralizing and sharing your API descriptions, test suites and plans, the various ad-hoc queries people usually keep in their notes or on Slack (and lose), handling involved auth stuff which is a hassle with curl, etc.
I think they gravitate towards the same area as swagger.io or stoplight.io, but from the direction of using the existing APIs.
API registry is a useful tool with modern love for nanoservices when a team of five somehow manages ten of those but I don't see anything similar done by Postman. Two of the service registries I know of were implemented in-house for obvious reasons.