Well, that is just my (educated?) guess, of course.
But in the Lejendary Adventure game, having the Chivalry skill not only gave you knowledge of noble manners and such, it also gave rather large attack/damage bonuses for combat!
(I guess that non-nobles would have to resort to ignoble tactics like using bows/crossbows/slings/staff slings, traps, or trickery to defeat nobility! Or perhaps a heat metal spell would work very well instead
)