I think it's just a logical and clear place to set a benchmark -- you can use as much safety equipment as you like to keep yourself safe, as long as you don't u

I think it's just a logical and clear place to set a benchmark -- you can use as much safety equipment as you like to keep yourself safe, as long as you don't use it to help you to get to the top. Historically, climbing safety equipment was very basic compared to what is used today -- a rope tied around your waist held by your mate at the bottom of the pitch might stop you tumbling down the mountain, but you don't really want to find out. In the UK, climbing culture is pretty conservative compared to other places (there's very little sport climbing here), so the (extremely sensible) attitude that your safety gear is for accidents not for helping you climb harder routes is quite prevalent.