Depends on where marijuana products end up on the regulatory spectrum. Vitamin E acetate is added to thicken the THC + solvent solution, because to users, a thicker solution appears to mean that the THC is less diluted than it actually is.

If marijuana products are regulated like supplements are today, there's really no reason why less than scrupulous vape cartridge manufacturers wouldn't do exactly what they're doing today. There's no regulatory oversight when it comes to supplements.