Yeah, I think Overrun is a little wonky and doesnt' need to be there. Disarm is pretty sword fight iconic for me though.
After thinking about it more, I think it has a bit to do with the way monster npc are created. If the numbers are just thrown down as you need them. When the baddie loses his weapon and you have to recalc things and have to start looking at well was he proficient with that, what's the proficiency bonus of a fist vs what he was just weilding, it could grind the game to a halt.
I guess it's just easier to say you can't do that.