Carrot myth in World War II Britain?

I understand that the British government promoted the notion carrots could help mitigate blackout blindness, which turned out to be a myth -- carrots can improve your night vision if you are Vitamin A deficient, but not otherwise. But why did the government promote this view? Was it to fool German pilots (and conceal their newly developed radar)? Or to persuade the British people to eat the massive quantities of carrots that would otherwise rot?