The reason I omitted it was the difficult problem of explaining a complex subject in very few words, and still pointing the finger at banks. If you tell joe six-pack that his mortgage sometimes got cheaper you'll either have to divulge a complex explanation of why this is bad for him (which he won't understand or care about) or have him think that the banks should do some more of that LIBOR rigging so his mortgage can be lower.
It's a compromise.
