Or perhaps, by not banning it, it's not being seen as a "fobidden fruit".
There's also the cynical belief among most who favor the WOD that everyone is a potential junkie, and we only have the laws prohibiting drugs to thank for preventing everyone from running out and getting stoned.
Those of us with a little better reasoning skills realize this is not the case, and the fact that there is no massive problem of spray paint sniffing only verifies that.