Although most phones have a data plan from a cellular network provider, a network connection will most likely not be available at all times. In fact, in some areas it can be difficult staying connected to a network. Therefore, it is imperative that your app is engineered to be resilient to network disruptions.
Furthermore, awareness of the type of network connection that the device is using allows you to tailor the volume of data traffic that it uses. When connected to a local area network via Wi-Fi or a USB cable, it may be acceptable for an app to download large data files. Conversely, depleting a user’s cellular broadband connection by transferring a lot of data is probably not acceptable.