Most smokers I know will carefully separate their trash and walk hundreds of meters to put everything in the right bin... and yet dispose of their cigarettes all over the place. To my shame I have to admit I was one of those people. Somehow the inconsistency just didn't cross my mind. So many other thoughts took precedence. I'm not saying that this is an excuse, mind.
I do understand the anger and frustration, but I think it's both fairer and more productive to assume that people are not doing these things to intentionally cause harm, and that they might well be upstanding citizens in other areas of life.
I don't fathom how you don't/didn't notice, it's like throwing bubblegum wrappers on the ground, yeah its small, but when you smoke packs of cigarettes in the same spot it adds up, not to mention more of a hassle to clean up by others like picking up confetti off the ground. I'm glad you realized it, but I can't imagine how people are utterly clueless about it being a problem (I just assumed all smokers were a-holes because they didn't care).
The net-net is that people rationalize their actions using whatever means necessary.
1. https://en.wikipedia.org/wiki/Tragedy_of_the_commons 2. https://en.wikipedia.org/wiki/Diffusion_of_responsibility
I say this as the weird guy random walking the parking lot, picking up trash and transporting it to the wastebin.
The single mom in your example may have had little parenting because her mom was working 3 jobs perhaps.
Anyone else remember the "don't litter" public service announcement on TV with a crying Indian?
If this is the case, it would be interesting to find out whether there is some correlation between wealth inequality and rates of littering.
One example I keep seeing is people who buy a pack of cigarettes, rip off the plastic film covering and just drop it on the floor. It sends me into a silent rage every time.