I submit that when thinking about what leads to different outcomes between people, casual observers (more or less consciously) turn to themselves and ask: "What differentiates between those different outcomes within myself [e.g., between different days]."
For example, when you observe the quality and quantity of your work output, you are going to find that you are much less productive on days on which you are (i) tired; (ii) plain lazy. In contrast, your general talent is, by definition, constant between days. It is hence tempting to conclude that what differentiates productive from unproductive people is energy and work ethic, while talent is rather unimportant. This explains the popularity of the received wisdom about inspiration and perspiration.