Psychology plays a big part in the 'addiction' of smoking. And when it comes to switching, the idea that one is sacrifcing something (rather than gaining something) can be hard to overcome, especially if the first day(s) of vaping have difficulties (no spares, wrong juice, technical problems, etc). That said, it is quite possible to have a perfect vaping setup, know that vaping tastes much better, know it's healthier and doesn't risk a fire, leave bad smells etc etc and yet still know that something isn't right; not everyone but some people - there's just something biochemically out of balance and not everyone can just tough it out for a few months.
In the absence of a WTA option, such people, i suggest, need to take a long view; cutting down slowly over quite a long period; and try different vaping regimes as assistance (with or without nicotine). Or try snus.