Why does Rey Mysterio continue to wear a mask even after being unmasked in WCW?

ACTUALLY, Rey Mysterio JR was unmasked. Rey Mysterio was his uncle's gimmick, and he formally asked him if he could use it. SO, WCW was Rey Jr, and he was unmasked, but when brought to WWE he used a new gimmick.....with a mask, even though it's the same damn thing, but that's what happened.