> No, it hasn't. The only reason I use mpv instead of VLC is because of the frame step feature
You realise your requirement is important for less than 0.01% of users? For every requirement you have to balance future maintainability and the impact it has on the code base against potential revenue
I assure you the figure is much, much greater than 0.01%.
Even outside of specialist uses (and not just in the field of video, either), most people like being able to pause a video on a specific frame to be able to study it more closely. Often that requires (or at least the task is made much simpler by) being able to step forwards and back frame-by-frame.
You realise your requirement is important for less than 0.01% of users? For every requirement you have to balance future maintainability and the impact it has on the code base against potential revenue