Sketch heavily relies on Quartz/Cocoa, which is Mac/iOS only. Both are very powerful and allow devs to produce high quality graphics apps with relatively little

Sketch heavily relies on Quartz/Cocoa, which is Mac/iOS only. Both are very powerful and allow devs to produce high quality graphics apps with relatively little time and manpower. Had they started out cross platform it’s doubtful they’d been able to achieve what they did when they did.