Charging per-use prevents inefficient use (very small loads in large machines) and tenants letting their friends use the machines, eventually turning the laundr

Charging per-use prevents inefficient use (very small loads in large machines) and tenants letting their friends use the machines, eventually turning the laundry room into the free neighborhood laundromat. Some buildings have switched (decades ago) to reloadable laundry cards to avoid having to deal with change.