The problem is how it makes you and your surroundings look and smell.

Then there is:

The digging in the trash for a butt at 3am like some kind of starving rodent. Having to stop on road trips and stand outside in a fucking blizzard just to take a couple of drags. Scrubbing your fingers with steel wool and comet to get rid of nicotine stains. Taking your $200 slacks to the cleaners and asking them if they can fix a burn hole in the crotch. Taking your car in to see if they can fix a burn hole in the leather seat under your crotch. Swerving in traffic and risking your life and other's while your crotch is fucking on fire....

It might be healthy but its not worth it.