Its all about portability. You can easily use these oil carts at theme parks, concerts, walking through your neighborhood without stinking of weed. Not only that, but they were getting real cheap (which could also be because they are black market). Dank Vapes carts were being sold for $25 to the end user (not wholesale). No way you are selling at that price without cutting corners in production.

So young kids see $25, no pipe/papers, ease of transport and hard to get caught.