Because this is a different game and has its own gameplay. We're styled more after o2jam/djmax which have SV changes than we are Stepmania. This certainly wouldn't be rankable and I'm not even considering this as a mod right now just because I don't feel it's right - I think that players should play maps 'as the mapper intended'.
If you want no SV changes edit the map yourself.
If you want no SV changes edit the map yourself.