The thing is that psychology gives us ideas that shows how humans can be influenced individually (think foot in the door or an incredible offer that ain't really an incredible offer). Sociology gives us ideas of how humans can be influenced in groups that, in literal terms, will give away their freedom and rights with tears of happiness in their eyes to a charismatic speaker who says the right things in hard times.
How does supply and demand fit in all of that when the assumption in the model is that we behave rationally? How does the work on habit formation fit into that? How does peer pressure?
I smoke cigs. I pay for take out food and chocolate. Before I got a car, I'd get a cab to work even though I had a bus pass. Now I'm not holding myself up as a model of the actual man but that's the point: the homo economicus is like the description of someone's ideal of homo sapiens. Ideally, that's how we should make decisions about resources. In actuality, I think it's just far off the mark to cause what would be sound decisions to work out not so well.
Economics to me is like a social science trying to be used as a hard science and in a position to be quite dangerous.
It seems to me that optimizing for aggregate demand or aggregate supply will merely result in redistributing to politically connected individuals who are able to convince the authorities that their programme will improve that metric.