That's a vaporizer, it already doesn't completely vaporize the THC because the surface area that it applies heat to is not constant, it's inefficient af. He puts that vapor into a percolator bong, which makes the vapor dissolve in the water more efficiently(because percolator are made for smoke, not vapor, and also, vapor more readily dissolves into water, since it's not smoke and is at a lower temp)

All in all, through this contraption, you get a jizz trickle of vapor that is barely the equivalent of the amount of weed used to generate that vapor.

Just because he could, he didn't stop to think if he should