People like that seem so blatantly dismissive and disrespectful, which on it's own should indicate a lack of awareness or consideration, plus I doubt anyone that ever "forgets" is ever actually incapable of "getting it" when it's just telling the difference of ONE and the OTHER. It's very simple, I think it's j a buncha excuses for laziness or unreliability.
Some people will defend it and say "well they all go to same land fill anyway!" and they're right (for the moment only), but it's also just hard to blink past their "not my problem" attitude. We *will* get better at recycling tech, and when we do, it can only be of benefit to the world (that we all collectively inhabit...!) when the trash is pre-sorted.