That’s not a great comparison: the two tools have very different users, and if you’ve ever used Postman for anything non-trivial you’ve probably hit things which are but should not be substantial points of friction (secrets, OAuth renewal, diagnostic output, etc.) whereas Dropbox really did a great job of doing exactly what you wanted with a minimum of fuss.

Well and that's it right? They get developers on board early, and techies, etc... then shift to mass market and remove features and add anti-features.

Github, slack, whatever else. it's a big long cycle. Now I see tools like Postman and the first thing I think is "how do they want my money, whats their strategy financially", things I never thought when I bought a CD-ROM or a one-time license to tools.