We as a society will not tolerate people throwing rubbish into the street. Napkins, newspapers, paper cups, we've trained people to throw those into trash cans or other suitable bins.
So why is there an exemption for cigarette butts? Look around any bus stop or park bench, and you are likely to find a little mound or scattering of cigarette butts. People will flick them out of car windows, or drop them on the ground as they walk by (if we are lucky, they'll take a moment to squish them under a toe to ensure they are extinguished).
It's a filthy, disgusting habit. I can't take my baby to enjoy the park without watching to see that he doesn't pick up cigarette butts (and he is at the stage where he puts everything into his mouth). I see soggy paper and filters around bus stops and city streets.
It's your mess, don't leave it for someone else to clean up!