Part of the purpose of quitting smoking, is no longer being addicted to a drug. We all had such trouble quitting, because the nicotine was so highly addictive. Just think about how it felt, all those times you tried to quit cold turkey. So you must admit, that part of the reason you quit, and why you kept smoking, was the addiction. The addiction is tied directly to the negative health effects of smoking, because if you weren't addicted, you would have been able to quit much easier, and we wouldn't have nearly as many vapers as we have today. Also vaping may not have ever been needed, as quitting cold turkey would have been a lot easier.
That said, why do so many vapers (probably nearly all of you) continue to just vape at whatever nicotine levels you were smoking at? Its so easy to just ween down now. I started at 18mg, (iirc) and slowly, over time, got down to 0mg. This did take a few years. But I did it. There are plenty of places out there that will let you go in intervals of 2mg, up or down. The place in town where I buy most of my vape juice also does this. I went down to 16, 14, 12, 10, etc etc until I got to zero. If for whatever reason, I can not vape, no big deal. So why don't most people do this? Why would you want to remain addicted, so that if something happens where you just can't vape, you go into freakout mode? Its actually disgusting to watch. There are plenty of situations that could arise that could prevent you from being able to vape, possibly for days at a time. Nicotine has also been linked to stomach cancer so that's another reason.
I think you assume people want to stop nicotine. This is similar to asking why someone doesnt just stop drinking coffee in the morning
Most people that want to quit, either want to quit due to health concerns or through stigma of anti-smokers. That said, most smokers dont want to quit.
You're also making an assumption that it's nicotine that everyone is addicted to. Check out DVap's blog here and learn about Whole Tobacco Alkaloids: E-Cigarette Forum - DVap - Blogs
There are things in analogs, more than just nicotine, that are addictive and have effects on us. Some to such an extent that vaping wont help some smokers, WTA is the reason (and there are 2 companies that sell WTA ejuices)
Those of us that wanted to quit for health reasons; dont really want to give up our habits, nicotine is relatively safe and it's effects are enjoyable. So why stop the fun if you dont have to? =)
That said, I did ween down from 24mg down to 6mg. I dont think it's a proper weening though. I started at 24mg in the Kanger T3's that my ego starter kit came with. As I moved to gennies and more advanced RBA/RDA's I found I was taking in more than needed and found 6mg gave me the desired effects.