nicotine is a whole other story.
nicotine IS needed. it allowes people to get the nic fix they NEED in order to stop smoking. nicotine is required in order for vaping to work as intended, and get people off cigarettss.... D/AP is not.
nobody says "man i need my D/AP fix" or "i wish i could stop smoking, but this eliquid just doesn't have enough diketones for me."
You are making a legitimate point here, but IMO, not making it accurately. I've quit cold turkey prior to vaping (for longer than any vaper has quit smoking thru vaping), so to say it is needed (with all caps) is in my strong opinion, plain wrong. I grant there are many vapers who feel this is true, but to the degree this becomes 'truth' it just plays into the medical model for vaping. We live in the (legal) world where vaping is recreational. For survivability of the industry, we would do far better politically if we demanded no nic juices and then just let people add that in, as may be desired.
Thus not really needed, but is very much desired. I desire it. I'd like vendors to keep adding it, and keep disclosing how much they are adding. If one company came along and produced the best eLiquid I ever tried, but refused to disclose nic content, I'd either avoid their liquid (likely) or possibly test it myself and based on that info, would decide whether I continue to use it.
If great tasting flavors can be made without DA/AP, and that guarantees less harm than very little (and I emphasize guarantee), then I think the industry will move in that direction. I don't think it will happen solely (or even mostly) because of FDA. I do think the anti-DA hoopla will play a big role, but I'll be looking for that guarantee and if harm does occur, I'll be sure to point out how wrong you all were (including Dr. F. and Kurt).
Vaping is clearly popular because of the multitude of flavor offerings. Some vapers have moved to unflavored, and seem to really like it. If entire industry moved to unflavored, and issues of harm are still on pace of what they are now (read as very little to none, while anti types roar loudly), then I think smoking will bury vaping within 5 years or less. There will always be vaping/vapers, but growth will no longer exist. Fortunately, I think there will always be a market for flavors (even if underground), so really is unlikely we / the industry goes to place of unflavored is best way for all involved.