No labor required for taking on fuel and water. Needs no attention while idle, because there is no fire to watch or water level to keep up. Ready for service at any moment. No time wasted or water needed for boiler washing. No standby loses.
Cheapest labor can operate, and can be released for other work when locomotive is standing.
No waste of steam through pop valves or operation of injector. Less labor required to keep locomotive clean. No smoke to soil buildings and products. Hauls heavier loads than standard locomotive. Easy work for operator, which makes him like his job.