"Coolers" work just as well to keep things warm. I use them for sous vide, for example.
I was waiting for this and you're right. Yes, I have sous vide as well and also smoke pork shoulders and briscuit. I'll wrap the food and put it in the cooler to keep it warm and let the steam do the work... mmmm. But I would bet when most people think of Igloo coolers, they think of keeping things nice and cold.