The danger of something is not the only factor in banning it. It's the danger : utility ratio. Cars are dangerous, but their utility is very high. Guns are also

The danger of something is not the only factor in banning it. It's the danger : utility ratio. Cars are dangerous, but their utility is very high. Guns are also extremely dangerous, and their only utility is their danger - they are made to kill people (and protect, as a side effect). We ban guns because we consider their utility low compared to their danger (replacing them with police and a civil society).