The point is: living on 0.5 * $annual_income requires discipline. If you give 0.5 to charity, good for you. If you put 0.5 to a retirement plan, or apply to so

The point is: living on 0.5 * $annual_income requires discipline. If you give 0.5 to charity, good for you. If you put 0.5 to a retirement plan, or apply to some long-term debt that you assume, good for you. Not everybody has the discipline to get $10 and only look at $5 as "available".