Why are cigarette butts the most littered item on earth?

Abstract

"Since the 1980s, cigarette butts have consistently made up 30 to 40 percent of all items collected in annual international coastal and urban cleanups. That means cigarettes, which also top America’s list of most littered things, have the longstanding distinction of being the most littered item on earth, with about 4.5 trillion cigarettes discarded each year worldwide. Why does cigarette litter remain so commonplace, even in the U.S., where smoking rates have gone down? Three factors help explain".