One reason I’d imagine that with the drum machine if the top final limit failed, the cab would be pulled up into the overhead without a means to stop ending in a possible free fall of the cab and ultimately a rewinding of the counterweight back up. Sounds like a bad call back huh?
Single or double roped cabs and counterweights dead ended on the drum had to give way to the more modern traction machine as technologies were developed. Why they’re still legal is a good question. You’d think they would have gone the way of the belt driven vertical man lift a long time ago.