You'd be surprised, maybe horrified, if you knew how many people primarily interact with the Management Console instead of the CLI or the SDKs. In-browser terminal sessions are a real convenience to that special kind of user that hasn't (or won't) take the time to learn a modicum of productive CLI skills, but has the occasional need to SSH in.

On the GCP mobile app for example, not all feature is exposed, but there is a cloud shell, with which you can do pretty much anything you want.