Final Fantasy/Luck
Luck is an attribute that comes into play when no other statistic applies. The most important function of Luck is the ability to run away from a difficult fight; it is no surprise that the Thief has exceptionally high Luck scores. Often, the Thief is included in a party simply for his ability to escape to safety.
Being able to run away from battles is extremely useful in the game's final challenge, the marathon Temple of Fiends.