[andymcsherry]

I think what I've mention already should outline the impracticality of your suggestion. It's hard to distinguish between a cigarette that's fully extinguished or not. This is why ashtrays are made of glass or contain sand, you can't set it on fire. Smokers are easy to demonize when you don't understand their dilemmas. Don't worry we're pretty used to it. Most smokers I know understand their habit bothers people and do their best to not cause a burden on others. When society has set up rules that make it impossible to do something properly, don't be surprised when people don't.

[BHSPitMonkey]

So smush it properly with your shoe and then put it in your pocket until you get home or find a worthy receptacle. If I have a granola bar wrapper in my hand and there's no trash cans nearby, I don't throw it on the ground; I hold it in my hand/pocket/bag until I can dispose of it. Cigarette filters are not a special case in this thinking.

[spditner]

There is a category of products to help address that called a "portable ashtray", they can often clip on your key ring.