It'd be useful for clients that are authenticated through some sort of portal with either a data or time restriction to be able to see how much data or time they have left without someone logging into the controller to check the Hotspot page.

It could be part of the Omada App, and the login page gives you the option of client only view, which just checks your MAC against the Authorized Clients list, pulls the data, and then shows it on screen, possibly with the IP Address and MAC address of the device so users can provide that information to the Admins over the phone without Admins needing to explain where to get it from the Settings menus of a phone.

Another option is a standalone app, or a local webpage on the controller that does the same thing.