FUE using donor hair from body

[Thinning@30]

Does anyone know why FUE can't be used to transplant donor hair from the body to the scalp? Doesn't hair transplanted from other areas to the scalp take on the characteristics of scalp hair?

I've been wondering about this lately, and I'm sure there must be reason, but I don't know what it could be. It seems like the primary concerns most have about the FUE procedure are the resulting pinpoint scars, and the risk of transection of donor scalp hairs, which would make them useless. I imagine most men have plenty of body hair in places where they would never miss it, and wouldn't be terribly bothered about FUE scars in these areas (think legs, armpits, etc). Why not harvest from these areas, and so what if a few of these hairs are lost to transection? Just wondering.