Why Use a Boot Dryer?
Winter: Damp boots are COLD
Summer: Damp boots are STICKY
Any time: Damp boots get STINKY
If you need to know more, do an internet search and you can learn all about sweat glands, bacteria, and fungus; more than you want to know.
But you will learn that YOU WANT A BOOT DRYER! So get a good one!