It's probably just not very cost effective, or the climbers don't give enough of a fuck to want one... I mean, if OSHA allows it, it can't be that bad lol. And, have fun engineering a sliding anchor point that freely moves in 2 directions for 160 feet unless its pulled on at x speed/force level, and then pitching it for every sattelite tower construction company in the US.. I dont think anybody wants to be the guy who bids jobs costing 10% more for a safety precaution that isn't necessary. If you don't feel okay climbing it, get another job. It seems like these guys have no issues with it