Why is the windows version so behind (v5.7) from the iOS version (7.7)?

I really like the feeling of drawing in Fresco (although it lacks a lot of features and forces you to stay online whether you want to or not). But the most annoying thing about Fresco is that the iOS version has a lot of features that are not in the Windows version. And it’s not a matter of months—it’s years behind the iOS version.