"doesn't inhaling nicotine cause many health problems on its own?" Not really. Nicotine seems to be about the same or maybe a few times as dangerous as caffein

"doesn't inhaling nicotine cause many health problems on its own?" Not really. Nicotine seems to be about the same or maybe a few times as dangerous as caffeine, which is to say barely dangerous at all. Most of the danger of cigarettes is burning the plant material. There is a study assigning cancer risk to the toxicants of tobacco smoke and there is a list of the top 50 or so chemicals of concern called the Hoffman analytes. Nicotine isn't on this list.