NEED? No, it's entirely possible to clone without any rooting hormones. Cloning powder is not common out in nature, yet plants are still able to clone themselves. Also, there are plenty of successful cloners out there using aeroponic methods with great success (and no hormones).
DOES IT HELP? Yes. Rooting hormones lead to faster and more successful cloning when cloning in a medium (i.e. not aeroponic).