I think your final point is the answer. "Affordances" are just cues. And a cue is just something that says that if you engage in a specific behavior, you will earn reinforcement or avoid punishment. In the case of crumbs on the counter, you're probably avoiding the punishment of mice and roaches in your house. Probably training men to respond to the same cues we were trained to is a project most of us don't have the time, patience or skill to do, but we can provide other cues, such as a big sign "Crumbs on the counter? Please wipe them up." Etc.