Yeah that's true. It seems like people mostly just "chase the dragon" as the de facto, go-to routine de jour. @axe battler is correct that tar heroin will leave behind some nasty residues that polymerize and will not leave a piece of glass until it is soaked in sodium hydroxide (lye) solution. Foil is cheap and easily procured and thrown away.
Having said this, I don't see any reason why someone couldn't vape H from a dab rig, e-nail, e-dabber, or theoretically even an e-juice vape tank and mod battery setup. I guess my concern might be for the stability of the diacetylmorphine molecule in an alkaline state without the protection of an acid molecule bound to it and rendering it water-soluble with a higher boiling point.
Though you would yield less product, I suppose it's also possible to perform an acid/base extraction of that #3 heroin to move through #4 heroin and then back into a smokable freebase form that's even cleaner than the preceding two forms. Takes a little technical know-how, but it's a very attainable goal. Just keep in mind that you'll be removing impurity weight.
Oh I'm not sure, but that sounds reasonably accurate. Yes, the same extractions would work to isolate the 6-monoacetylmorphine, but obviously you're gonna need some acetic anhydride to react with the 6MAM to produce diacetylmorphine (Heroin). In the case of someone smoking this though, I'm not sure that's gonna matter much as the body metabolizes diacetylmorphine into 6MAM anyway. The main draw of Heroin is that the presence of the two acetyl groups on either side of the molecule has something to do with its rapid absorption into the body, making it most prone to an intense rush when taken intravenously.
You take a straight glass tube and torch the end of it (with a torch) until it's red hot. Then you have your heroin in a little silicone container. Any of the little rubbery stash containers with lids works. Then you tap the red hot end of the glass tube on your down and it will melt and you can smoke it through the other end of the glass. You're not smoking foil and it doesn't burn up and waste as much as on foil.
There are such things as heroin bongs too. Pretty much the same as the glass tube, you heat the bowl piece of a bong with the torch til red hot. Then you have your heroin hopefully sticky on the end of a small knife. And tap it on the red hot bowl piece. To take a bong hit. You don't even need the actual bowl piece to the bong just the bowl piece stem that goes down into the water.