It's a good question -- quantifying this is exactly the problem. The media hypes something, and all of a sudden the banning hysteria kicks in, with no rational investigation about whether the product is being used mostly for legal purposes. To come full-circle, hemp was mostly legit use before it was made illegal. Even though one can apparently extract hash oil from it, it was much more widely used in textiles. So by your criteria (mostly used for legitimate purposes), it shouldn't have been banned, correct?
I'm not aware that it was banned. It just went away.
You can google up any 'History of Hemp' site and you'll see that hemp was a dead industry just after the turn of the 20th century. It rebounded during WWII when we couldn't get it from overseas, but then it quickly died again.
Quite frankly, there is no reason for it to be making a comeback, other than one.
But hemp is not banned for textiles or any other non-human-consumption uses. Growing hemp is legal; however, it requires state and DEA licensing.