Could be a few different reasons.
1. Your phone and your tablet run different versions of Android and RC didn't flag the app as being compatible with the version of Android on your tablet.
2. RC deliberately marked the app as not compatible with tablets because they (or most likely the firm they outsourced the development to) developed it with a phone interface in mind and didn't design a tablet-friendly user interface.
3. Tablets usually don't have the voice and texting capabilities that a phone has. When you build an Android app, you mark it as whether the voice and texting capabilities are required. If RC marked them as required (or more likely forgot to mark them as not required) you won't be able to install it on your tablet. Even if you could force the app to install on your tablet, if the app assumes that voice and text capabilities are present, it will pretty quickly crash.