It adds more feel to the Clockworks, as for some reason if you do a thousand Clockwork runs you never see a trapped knight, but go on one mission and you see half a dozen of them.
There's also the awesome duel between monsters and invincible noob knights as well.
I had this idea too, but I'm going to post another thread because it's just not right to stick a noob NPC knight to someone that doesn't want to carry it.