Currently both shapeshift native and keepkey users need to re-connect and unlock their wallet on each session. By caching a wallet's xpubs, users can view their portfolio and do everything in the app other than signing a transaction/message. The initial process of syncing a wallet seems to be resource-intensive and adds multiple seconds before a user can get into the app and do what they want to do (which more often than not does not include executing a transaction). Eliminating this step could potentially make the app load faster because its not re-deriving addresses on each load (and you can see when starting a new session that the app begins to load balances before kicking user to the connect/unlock wallet step), but it will undoubtedly make the app feel faster.
This also paves the way for supporting Watch Addresses/xpubs, Custom Bundles of Addresses/xpubs, and the ability to view cold storage balances (or any arbitrary wallet/contract) in the mobile app.