All smokers (nearly all), begin as kids to look cool / fit in. Most kids get sick when first starting tobacco use, so it's that important to them that they look cool / fit in.
After becoming nicotine addicted the fun begins........bad for health - lungs, heart, oral, other respiratory, etc
Bad socially - you stink, you need to get away from people / situations to smoke, you hang out with other losers who smoke, you become fidgety in social settings when you can't use tobacco, non tobacco users avoid you like the plague, etc.
The unnecessary expenses - a pack a day + lighters + gum / mouthwash (to conceal funk) + time loss (buying cigs, smoking cigs, etc) + higher health insurance & health care costs, etc
Btw, Thank God I'm tobacco-free since April 22, 2011.