The App is a fail from EasyEquites. Their official reasoning for doing this is so that they can push updates to the site and it will immediately be available for everybody.
The big tradeoff is user experience. If you ask me they did it this way because 1) it is cheap, 2) one less thing to support and 3) they only need the app approved once by the stores. Any future changes to it won't go to any of the app stores and won't be vetted.
The cost to develop also plays a role and, I'm speculating, but the dev house they use may not have the necessary skills (as in resources) to do it effectively.
To be honest though, who uses EE that much that they need an app for it?