Why? Because for every anti who might be offended by the word "cigarette" deeply enough to take action merely because of it, there are probably ten smokers who may be more drawn to the product because of the way the term "e-cigarette" (accurately!) suggests a smoking-like experience. I'm OK with "e-cigarette."
I really don't connect with the term "personal vaporizer." But I'm old and also don't connect with "personal trainer," "personal banker," "personal coach," "personal moisturizer," "personal space," or pretty much "personal anything."