With this pattern you can split your code in 3 main parts:
Model: Where you put your data
ViewModel: It's the logic of your app and a link between the Model and the View
View: It's the UI of your app (usually written in XAML)
Usually a desktop platform has a lot of available resources so many developers tend to avoid to improve the quality of their code. On a mobile platform the resources are quite limited and improving the code could make a huge difference. It can transform a slow and annoying app in a great fast and great one...