Based on my entirely anecdotal evidence:
* I know one smoker who also vapes
* I know one smoker who switched to vaping before going back to smoking because he found it hard to limit his vaping (because number of cigarettes is easier to measure)
* I know several vapers who either don't smoke or gave up smoking in favour of vaping
* I know several smokers who aren't interested in vaping
None of them is younger than 25.