The US has deep seated Puritan roots that have surfaced in the temperance movement that led to prohibition, the war on drugs, abstinence only sex education, anti smoking campaigns, and now the anti vaping campaigns. Under this view, the use of any substance is a moral failure, and the negative consequences that usually accompany habitual use of a substance are taken as a vindication of the Puritan view and proof of the moral corruption of the user. This mindset can't accept that there may be a way to habitually enjoy nicotine with few or fewer side effects. This mindset will never accept vaping as a positive alternative to smoking, no matter how much proof there is of reduced harm. It's not about public health under this view, it's about public sin, and nicotine will always be a sin to these people, even if you could make 100% healthy.