Liability is a very complex matter, and there are many things which cannot just be left to common sense.
If I install an aid for my own use, and leave it in place, and do not encourage (or discourage) others from using it, then one could say that anyone else using it is doing so at their own risk.
If I install an aid on behalf of a group of people, whether a club, or the BCA or whatever for the express reason that it is there to benefit third parties (i.e. other cavers etc), then it is important that I am sure the job has been done properly, and is safe when used in the proper manner. If someone uses it in an improper manner, then I would say they have only themselves to blame, unless, of course, I have provided them with misleading or poor instructions.
It is also important that the body who has arranged for the aid to be installed makes sure to the best of their ability that it remains in a safe condition, or if if becomes dangerous it is removed or rendered unusable.
A fault in a manufactured or artificially installed item is not necessarily going to scream at everyone passing by "look out, I am going to fall apart the next time anyone uses me".
What's this got to do with some guy dying on the road? Not a lot.
I do not condone the death penalty for what he did, so why should I be happy when he dies in a car crash?