Although today, we consider this phrase to be about household income, it wasn't exactly that way in the beginning. I'm personally convinced that this idiom was coined by boxers or by people in the boxing world. "Bring home the bacon" meant "win the boxing match." Of course, it also meant, bring money by winning the match. And over the years, the phrase started meaning income in general and people now use it for all occupations. So it has become very generalized.