Because you get no tar
It's basically like vaporizing in a convenient cigarette.
And as far as I know this should work, propylene glycol is an alcohol (I believe, please correct me if I'm wrong) and as you know THC is alcohol-soluble. You shouldn't even need to boil it this way. Unless the propylene glycol doesn't activate the THC, then yes you need to boil it.
Do E-Cigs burn the contents or heat it up at all?
Yeah that was my theory. I thought i'd need to boil it to release the THC but as you pointed out it is alcohol soluble. So just the PG + bud would work? I wouldn't need anything else?
And for those asking why i'd want to do this... there are many reasons.
1. Portability. It's the size of a cigarette, only looks more sleek.
2. No smell
3. It's healthier. You're vaporizing, not smoking. Because of this, you also get a more clear headed vape-esque high rather than the lazy headache high from smoking all the tar.
3. No need to light it... all you have to do is inhale
4. If a cop searches you and finds it, he can't do shit. Just say it's an e-cig. He won't know whether or not the murky liquid is actually THC+PG rather than nicotine+PG. Like I said, there's no smell. In fact, you can use it while talking to a cop.
5. It comes with a case shaped like a cig pack that charges it on the go, and holds extra batteries and atomizers.
Honestly, to me, it's hands down the most perfect toking tool I can think of. All the pros, and none of the cons.