This decision is hard to justify on the basis of scientific evidence of harm. Despite the tobacco industry's decades-long effort to deny the link between lung cancer and smoking tobacco, it seems well-understood that the combustion product benzo[alpha]pyrene plays a major role. This is one of the polycyclic aromatic hydrocarbons (5 rings in this case) which, after being processed by lung cytochrome p450 enzymes, will form mutagenic DNA adducts. Adducts that form in regions of the genome that control the cell life cycle can result in cancers, particularly if defects exist in normal DNA repair mechanisms. For example:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268909/

Some of the enzymatic activity resulting in conversion of PAHs to activated PAHs capable of binding to DNA appears to be promoted by nicotine and inhibited by THC, curiously enough, i.e. the cannabis-vs-tobacco smoke issue:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1277837/

However, there's no benzo[a]pyrene or similar PAHs generated via vaping, it's just nicotine in an aerosolizable liquid (propylene glycol + glycerine) which doesn't seem to have any medical negatives. Juul also includes benzoic acid as a preservative to avoid microbial growth, however, which is something I'd avoid inhaling personally.

Nicotine is indeed a highly addictive substance, but there seems to be no scientific reason to allow smoking plain tobacco while banning vaporized nicotine. I'd suggest removing the benzoic acid, which would of course shorten shelf life and perhaps require refrigeration, if anything.