4 Greens, Capot's post #4 above has the main reason in its last paragraph: it's simply that rearward-facing seats are heavier. This is because the c.g. of the decelerating occupant is further from the floor, the moment arm of the decelerating force applied by the occupant to the seat is greater, and so the seat mountings have to be stronger and are therefore heavier... The accountants see rearward facing seats as lost payload and therefore lost revenue, and will not countenance them. In the absence of determined regulators, or a travelling public up in arms for them, they are just not going to happen.
Incidentally, going on leave as an indulgence passenger on a scheduled RAF VC-10 service many years ago, I was refused travel insurance by any company, even for a loaded premium, because I was not 'travelling with a recognised airline'. When I explained that No 10 Sqn's seats were safer than any airline's because they faced backwards, and moreover that the aircraft would be flown to and from Washington by the same crews who had flown the Queen the previous week, the answer was still no. We went to the USA without travel insurance. I concluded that the insurance industry's ignorance is matched only by its inflexibility.