I think it's because the butt is usually made to resemble some natural material like cork.
Since the rest of it (paper, tobacco, and ashes) is easily degradable, I think the natural assumption is the butt is degradable as well, and the notion that every other smoker seems to think so isn't helping.
So to answer the question: I suspect it's simply a lack of information. As a data point I'll add that I stopped deposing them right away a long time ago, because I suspected they might not be easily degradable, but this is actually the first time I've read this is the case.
If I'm correct I see no harm in correcting friends who smoke in their behaviour. They are simply unaware.
I would be interested in hearing from anyone who has been successful in this. I haven't tried educating again after a couple signal failures, concluding that people willing to harm themselves also don't mind harming others, or oceans. Probably what I should do is ask every smoker whether, out of curiousity, they know the butts are not biodegradable, since they're plastic. That sounds less like a lecture.
Even if they were biodegradable, why would that make it okay to throw them on the ground? Half an uneaten sandwich is certainly biodegradable. Ants or birds would probably dispose of it in days. But what sort of degenerate just tosses half a sandwich onto the sidewalk? That's inconceivable behavior for most people.
Even not being biodegradable, they degrade in a couple of years and wouldn't cover the shoulders of every road if the supply wasn't constantly being replenished.
Cellulose acetate degrades in between 18 months and 10 years depending on environmental conditions. A plastic bag can be there in 100 years.
> While it was initially believed that CA was virtually non-biodegradable, it has been shown that after initial partial deacetylization the polymer's cellulose backbone is readily biodegraded by cellulase enzymes. In biologically highly active soil, CA fibers are completely destroyed after 4–9 months.
Since the rest of it (paper, tobacco, and ashes) is easily degradable, I think the natural assumption is the butt is degradable as well, and the notion that every other smoker seems to think so isn't helping.
So to answer the question: I suspect it's simply a lack of information. As a data point I'll add that I stopped deposing them right away a long time ago, because I suspected they might not be easily degradable, but this is actually the first time I've read this is the case.
If I'm correct I see no harm in correcting friends who smoke in their behaviour. They are simply unaware.