[ Disclaimer, --- , ]
Taunting can trick an enemy into focusing on you, rather than other party members who may be more susceptible to damage and death.
It is also important to realize what taunt actually does. Each taunt has a small chance of moving the taunting player to the top of the agro list. A successful taunt will, thus, cause the mob to turn its attention towards that player. However this also means that taunting a mob which is already attacking you has no effect - i.e., it doesn't increase your amount of agro.