Ease and iteration speed for complicated APIs. Why make notebooks when you can just make a single python script?

Well, same way that notebooks are a REPL that remembers things, it's helpful to rapidly tweak parameters in your API calls, flick a menu to point to a different environment, retry requests on your own local instance, etc. Then when you have it all ready, you just save and it's shared with your team, and the non-developers don't even need to learn what a virtualenv is. Even your CI can take advantage of it. Well, it could.

There's "nothing" Postman provides that you can't do with a python script and git, but it lets you move much faster and have a tighter iteration loop.

That said, paying $10/user/mo just to effectively share a bunch of json definitions was always a plan that only made sense with corporate credit cards. With this added artificial restriction, my team is going to be looking for other alternatives.

Dropbox gave a similar degree of convenience and that's why they took off. But once every cloud provider figured out they too can sync files in the cloud, the novelty became a commodity. This plan reeks of Postman being out of actual feature ideas so in their desperation they're just milking whatever they can get out of their corporates through artificial restrictions before "a cloud-sync'd API runner" becomes a software commodity and the lights go out.