Not a smoker, but I was personally surprised when other people told me they'd have no compunction against discarding an apple core or other similar biodegradable trash on the ground.
Given that some people believe cigarettes are also biodegradable, that attitude may explain it.
As a society, we've also moved away from having appropriate storage for discarded cigarette trash - ash trays are no longer standard in anything and were already becoming a curiosity more than a decade ago. I assume cigarettes in a normal trash bin present a fire hazard and can't be disposed of there.
Given that some people believe cigarettes are also biodegradable, that attitude may explain it.
As a society, we've also moved away from having appropriate storage for discarded cigarette trash - ash trays are no longer standard in anything and were already becoming a curiosity more than a decade ago. I assume cigarettes in a normal trash bin present a fire hazard and can't be disposed of there.