The vast majority of people are unwilling/unable to think deeply enough about the system to understand it. Thus, the simplified rule of thumb that generating electricity reduces your power bill is needed for them to even understand the general direction of what needs to be done. Perhaps the power utility could include an explainer page at the back of the monthly statement for those with the interest and capacity to understand it. Maybe 2% of people will read and understand it. The other 98% can just be smug about their lowered power bill and blissfully unaware of their part in accelerating the market shift to solar.