I don't know why we have these less than lethal rounds if they are proven time again to be so damaging. Paintball guns leave welts and bruises just fine and don't maim you in the process. Take 30 paintballs to the upper body and you will be begging for mercy.
The complaint from police, especially with tasers too, boils down to that this needs to be strong enough to stop someone on meth with hulk strength. Police already have much more effective tools for this: Horse cop and lasso.