The thing is, no amount of experience meeting a payroll helps you understand issues that are critically affected by the way things add up at a macro level. Businesses are open systems; the world economy is a closed system, with feedback effects that are crucial but play no role in ordinary business experience. In particular, an individual businessman, no matter how brilliant, never has to worry about the fact that total income equals total spending [equals total production], so that if some people spend less, either someone else must spend more, or aggregate income must fall. [If somebody produces less, then somebody must spend less.]
This is why we have a field called macroeconomics.
I agree! That's why modern macroeconomics pays attention to supply, and not just demand, even while the average businessman may think that "more customers" are all he needs to be successful. And that's why it's wrong to expect policies that reduce production to increase spending.