It's probably just a historical artefact of the original codebase from years ago. I think it was also probably not covered because skipping frames implies wasting memory, since if you have loaded frames in to memory that aren't displayed, then it would be better to reduce the number of animation frames. I can see how it's still problematic if you want a dynamic animation speed that varies widely, though.
It's also difficult to change things like this without breaking existing projects, since for example if there are lots of projects out there that set an animation speed to 999 in events and just use that for a kind of maximum speed playback, then changing it to do frame-skipping will change how those projects work, and possibly break them.
You should be able to work around it by controlling the animation in events and using 'Set animation frame'.