> Because OSes can't provide a consistent API, app ship with their their own OS! (a browser today is essentially an OS on top of an OS). This. Even when targe

> Because OSes can't provide a consistent API, app ship with their their own OS! (a browser today is essentially an OS on top of an OS). This. Even when targeting a single platform the developer may very well choose to use one of these frameworks just to avoid having to deal with the most horrible parts of the platform in question (and GUI's tend to be those parts.)