Why aren't ladders used more frequently in hight building design for personel use? They're a cheap and efficient way of moving upwards for whoever wants to use them. If flow is a concern there could be built one ladderway going up and one going down, and they can have platforms each storey for safety concerns.

This design would be useful for buildings such as hospitals in which people flood elevators at the time for patient visits, using the stairs takes considerable more energy and you waste energy by using only your legs when your arms are available.