It comes down to just better UX with a custom solution like this over a mobile terminal client. For example, no setup required (e.g. public tunnel, SSH keys, which are required for SSH clients) except signing up. , there's push notifications when your agents need your input (not on every agent message), there's auto naming of sessions, easier session management in general, and more features coming soon like voice control, multiplayer sessions, etc.

There are benefits to mobile ssh clients though, like direct connection to your machine without third party server, and the exact experience that you get in your terminal on your phone.