Very useful for reverse engineering and security auditing of internal APIs. Particularly on Android a lot of apps pin CA certs or use their own trust store, so you have to do a little RE on them to insert your own cert... Or do it this way.
For a full bypass of that crap, you nowadays need a lot of resources including a Secure Enclave exploit - for now they're (relatively) cheap but eventually they'll be the kind of stuff traded for seven figures a pop.
Eternal shame on Google for not insisting that Android would follow the "PC model" of the user being root on their own machine and DRM and whatnot can go and screw themselves. They had the chance of actually delivering something that would not require jailbreaking and cat-and-mouse games like iOS, but they blew it (and blew the MAFIAA instead).
The funny thing is that they wouldn't have even needed to take this position. DRM works well enough on (e.g.) Windows to make the various studios more or less happy, and users have "root" on Windows as usual. Ditto for macOS. Hell, DRM works just fine on my Linux desktop install, as much as I despite its existence.
To be fair to Google, banks don't usually allow you to download and generate EMV tokens to perform card transactions on your PC, which places a different set of security requirements (legal requirements too) on Android phones for things like Google Pay to exist.
I might be less angry about that if there were a decent FULL backup solution for Android - with iOS I can do a backup and restore and almost everything will be restored, I think the sole exception is eSIM and Apple Pay because the secrets for that are in the SE. But for Android? Forget it, and there's enough games that don't even implement Google Play cloud-save integration. No way to backup these without root.