Why are terminally ill the prominent visual for quitting smoking?

I'm trying to figure out why someone who is terminal 
or disfigured by smoking related illness is a more 
convincing spokesperson for the cause than one who 
got free and now lives a healthy lifestyle. Scare tactics  
are not uplifting: Who believes that it really works?
"With my dying breath....? Really? Really?
Frankly, watching my Uncle Jack and Sister Chambier
in their hospital rooms deteriorate from cancer did not
make me want to smoke less- so worried and scared, 
I couldn't help but puff like an industrial smokestack.

"Free and Clear" should be the focus of role model.

Imagine a world without tobacco smoke...

This makes me want to breathe in the whole scene.

If you are wanting to quit, trying imagining yourself 
here for three minutes. Just let yourself be. Breathe 
the fresh air. Hear the waves. Feel the calm. 
Breathe. Take this time to be at peace.