"Just because a person doesn't have special abilities doesn't make them useless." Clark was only partly aware that Xander was a run-of-the-mill human, but so are his parents and all of his friends, and that's never stopped them from being useful. Or going up against meteor freaks. "My parents are completely normal, and some of the things they've done needed more bravery than I've got." Though he's slowly growing into it. But that's not the point.