Suppose you’re streaming music via your smart phone. Day in day out, you will notice multiple interruptions whenever the usage context changes. Only one mechanism used to transmit your data can be overloaded, such as LTE. This decreases the streaming quality significantly.
By using transition, however, the network automatically makes use of all available connecting mechanisms, such as LTE, Bluetooth or WIFI as befits the respective context of use. The result: Your connection maintains its high quality without any noticeable interruptions.