I looked around a bit across the net trying to find some details on what the luck/luc stat does, but didn't find many details. Someone suggested the following in another thread: "chance of resisting conditions and just a general modifier to everything else."
Given that luck is a "primary" stat for the thief class, I wonder if it has some positive effect on finding treasure or loot? I remember way, way back in Tale of the Forsaken Land, one of the guides on here suggested that thieves upped the chances of finding better treasure. Assuming that remains factual (if it ever was even way back then), I wonder if luck might influence that in some way.
http://www.gamefaqs.com/ps2/472311-wizardry-tale-of-the-forsaken-land/faqs/15494 [search the document for "note from Ndufer" if you're curious about what I'm referencing]