More you use an app the more space it takes up on iPhones and iPads?

I have an iPad and new iPhone 5 that I just got. I have rhapsody on both the same app and amount of music basically (iPad as seven more songs on app) but on the iPad the rhapsody app takes up 2.8 GB and the iPhone takes up 1.8GB. Why is that? The more use the app the more space it takes up even if you're not adding new content?

Nope, using an app doesn't consume gigs