They are used mostly for pulling carts and transportation. Although it is extremely unlikely for a mule to become pregnant (less than 300 reported cases worldwide), it is possible. They will tend to be cautious which may lead people to think that they are stubborn. They must know what they are walking on or what they are about to cross. They will be scared of anything that is not normal.
As trucks with four-wheel drive have become common, mules are little used for transport except in places without roads. They are shown in show against horses or other mules. They are used in western riding and English riding, and really good for high-jumping.