Because it makes my '63 SG/Les Paul a pain in the arse to play. It doesn't work as a vibrato, the string spacing is too close together, the strings hit the bridge at a shallow angle which I don't like and it kills sustain to my ear. I don't feel too bad about modding the guitar as it's already had a heel reset and a cavity crack but seriously, what were they thinking!! Anyone want to buy a sideways vibrola!!