"corporations preying on the vulnerable to do their dirty work."
I don't think these corporations are "preying on the vulnerable to do their dirty work", to quote you.
Even with those who can read, you will find that some will just ignore the signs on your letterbox. This behaviour is no different to those who spit in public places (despite the No Spitting in Public Place sign), or Don't Litter sign when some people are still throwing out their rubish out of their car windows as they drive along, especially on country roads.
