WHY

So  why is it that we humans always seem to be attracted to what is not good for us.  I mean smoking cigarettes as we all know can cause cancer,but yet alot of people smoke it.  Drinking too much alcohol is not good for us but yet we continue to do it.  speeding on the highway can be dangerous but yet we prefer to do it rather than drive slowly. so why do we continue to do the same thing we know can cause damage to us.  I just dont have an answer for this.  I hope someone out there has an answer.  Life is definetly weird and complicated.