People have to understand that before any new automated machine like ATMs, vending machines (and any product for that case) is introduced, thorough inspection and testing to face the real life scenario is done first. Only after they confirm to the standards, they are introduced commercially. People don't have to doubt it. The engineers have certified it. Some malfunctions do come in the rare cases-that's because of the fundamental fact that nothing's perfect, there's always a scope for improvement.