There was, and still is, actual recycling. I remember taking the (sorted) recyclables to a recycling business, which paid by the pound. I remember watching the homeless guys in LA pick aluminum cans out of the blue bins early in the morning on trash day, presumably for the money.

That said, I wouldn't be surprised if the single-stream version were largely marketing (by weight). WM or whichever company picks out a few things that are valuable enough to separate, then treats the majority as waste.