This same exact process is used in something known as an autoclave, which is a device that uses moist heat - that is to say steam - under pressure to kill off all living microorganisms on any object or surface contained within it.
The reason an autoclave uses steam is because steam is essentially the gaseous form of water. Water is able to transfer heat far more rapidly than dry air alone. I'm sure you know this if you've watched some survival show that mentioned the fact that people lose body heat far more rapidly in cold water than cold, dry air. Well, now you know why.