Bob R explained the same to me as we hiked past the cables recently. Apparently it was quite expensive to send a crew up twice a year to do the work, and the Forest Service has been dealing with continuing budget cuts for years.
If you look at the posts, you can see the taller pipes fit over smaller ones that are anchored into the rock.
If an avalanche hits them, everything will be bent over, and it will be a big mess!
