Going back to the original question of "why the AI doesn't use those moves?" I believe the answer is very simple. It would probably be a huge pain for TW to code it. I hope I don't sound too salty when I say this, but the AI in Bannerlord is extremely bare bones(or, to be more honest, just brain dead) as it is. Adding kicking and shield-bashing, with the prerequisite conditions for use would be a pretty major endeavor for TW, I believe.
Or to put it another way, if they can't be bothered to make an AI that utilizes the most basic of functions of attacking, defending and moving proficiently, I don't think they would be willing/able/both to make it use kicking and shield bashing effectively either.