. . over a fire. They don't work well on stoves because stove burners make the hottest part a ring well out from the center - the hotest part is supposed to be in the middle. You can't get that on a stove burner.
Woks are supposed to go on a clay "stove" with a hole on the top and a fire inside. I'm sure they work very well indeed with that kind of heating. I have some of the best woks ever made, but I'm still not impressed with how they work on gass burners.