Hmmm that's a good question. I think high school sports especially, encourages weight lifting for their athletes, even providing students and student athletes with weight lifting classes to educate them about different muscles you can work on and how to correctly do so. Personally, I think because of that, younger generations aren't so quick to think that weight lifting affects their height. In my opinion, I think it may be the older generations who sees the "danger" and the intimidating intensity of weight lifting. There may be a lot of sources where this myth could come from as well.