So, there are two related questions on that subject.
1) Why Mac? Because I'm an Mac / iOS developer and I know Cocoa. I have no experience programming for Windows (e.g., MFC, WinForms, WPF) nor Linux (GTK+ / Qt - I dabbled a bit many years ago but that's about it).
2) Why not use a cross-platform toolkit? Fundamentally, a cross-platform app is at odds with our core value - providing the best user experience. In practical terms, this means we have to use the native toolkit for the platform. While it is true that you can use a cross-platform toolkit, the experience will never be as good as it can be. Moreover, not only do I lack experience with such toolkits, if we want to make a cross-platform app, we would want it to feel native on all major OSs. This involves an incredible amount of work and resources that we do not have.
It all boils down to the fact that we want to make the best app for the platform that we have experience with.
1) Why Mac? Because I'm an Mac / iOS developer and I know Cocoa. I have no experience programming for Windows (e.g., MFC, WinForms, WPF) nor Linux (GTK+ / Qt - I dabbled a bit many years ago but that's about it).
2) Why not use a cross-platform toolkit? Fundamentally, a cross-platform app is at odds with our core value - providing the best user experience. In practical terms, this means we have to use the native toolkit for the platform. While it is true that you can use a cross-platform toolkit, the experience will never be as good as it can be. Moreover, not only do I lack experience with such toolkits, if we want to make a cross-platform app, we would want it to feel native on all major OSs. This involves an incredible amount of work and resources that we do not have.
It all boils down to the fact that we want to make the best app for the platform that we have experience with.
Hope that clarifies the reason why it's Mac-only.