There are thousands of narrow / bendy rural roads in this country where even in the most perfect conditions imaginable, it would still never be safe to drive that stretch at 60mph. What sense is there for the legal limit on those stretches to be higher than it would ever be safe to drive them?
BIt more time now so to clarify my facepalm, when I refer to conditions, I not limiting that to weather. It relates to the layout of the road, eg bends in the road, condition of the road surface, traffic etc, etc. I can't believe anyone thinks that when driving along country roads you are expected to drive at the limit and that's the reason why the are there. Common sense should be applied.