Ukenagashi= barai? At least that's how my sensei calls this move that you describe... i hope that its the same one.
Maybe we like it cause it effectively unbalances uke and we're suppose to be learning the blending motion of receiving/guiding the strike at the same time manouvering ourselves into a superior position.
Of course you could say that any skilled swordsman would not be unbalanced from a barai... maybe you're right. I guess it's just taught to show certain principles...