Postman's strength is not in the HTTP client part. It is in the SaaS part, ad I think their valuation (even though overblown) mostly reflects their corporate penetration and the willingness of many companies to pay a small amount for their services.
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.