Here in nebraska it is illegal to HUNT over it, not illegal to just put it out there. Law specifically gives a time period of when it has to be removed if you plan on hunting the spot (i believe it has to be removed 60 days before you start hunting). I've never used the stuff, but honestly, most of the private places I hunt, no one would ever know it was there. Its not like it sends up a signal flare for all to see.

So why do stores sell it? because they can, and people will buy it.