Second, throughput and latency. Every ~10 seconds, a cab for ~2 people arrives at each floor. That's a bit slower than if you press the button, the doors of a waiting elevator cab open, you get in, and it takes you to your direct destination. It's a lot faster than if you barely missed both elevators, and they stop at every second floor on the way up and down to let people in/out.
I wish we had one of these in our office.
Because people apparently like them and because replacing an elevator is an expensive affair.
It’s not clear that paternoster lifts are really more dangerous than standard elevators. The failures of safeties described can happen with standard elevators as well.
A paternoster can transport at least 12 people per minute (depending on the speed of course) per direction from any floor to any floor, more if their travel paths don't overlap or people ignore the "max two people per cab" sign.
Thus the continuous force to overcome is just friction.