I believe the question of legality when carrying a concealed weapon is an all different matter.
The reason you cannot make ilegal is that some people (read NRA loonies) keep trying to make look as carrying a concealed weapon is a constitutional right granted by the 2nd amendment. When it's clearly not.
That also doesn't mean it should be illegal... we've seen immense decrease in violent crimes over the past two decades -- we've also seen a dramatic shift in state laws allowing the right for people to conceal carry.
Correlation != causation and such, but science and numbers matter... They are really interesting when you review them.