You're being intelligent and rational, neither of which we can expect from the Govt or FDA.
My guess? Because its detrimental to BT and BP. It would solve the tax situation perhaps, but not those 2 big players unless they became heavily invested in producing better vape products themselves.
Like I said, I dunno? You might be Right.
I think if this was 2012, or even 2013, I could see it More. But I think Now that the Genie is kinda Fully Out of the Bottle. And Studies like the UK Health Ministry Study has given some Serious Pause.
I think the FDA will set a Bar High enough so that Only the Select Few can Jump Over it. But not Too High so that a Significant Vacuum is formed Enhancing a Larger Black/Grey Market that currently Exists for Regular Cigarettes.
Really their entire gameplan seems to be that every product they sell is *meant* to cause some other problem, so you'll need another of their products... which will cause some other problem, so you'll need another of their products... which will cause some other problem, so you'll need another of their products... to infinity...