Rebounding hammers are great on shotguns, where pressures are low.  You’re automatically on “Safe,” with the hammer in the halfcock notch.  But even in the black powder era, pressures in rifles could force the fired primer into the firing pin hole, or even allow it to burst,  if the firing pin was retracted.  Maybe not often, or with all ammunition, loads or primers, but guns have higher standards for reliability than a lot of things.   

Instructions for turning Hepburns into varmint rifles generally included grinding off the half-cock notch the hammer would customarily rest in, to allow at least the full mainspring pressure to hold the firing pin well enough to keep the primer from flowing.

Always seemed to me to be the waste of a perfectly good design feature; better to keep the loads modest (even “period”) and avoid the issue that way.