Weird discrepancy

How come it is "considered" ladylike to laugh at all jokes made by men but distinctly "unladylike," in the same universe, to vocalize your appreciation for a point someone has made?

Both guidelines as far as I can tell are supposed to make a girl seem passive. And yet, they are fundamentally opposite reactions. Why is giggling at a joke -- a way of flattering the person who uttered it: "you're funny!" -- such a girl thing while saying someone's made a good point -- clearly the same thing except: "well said!" -- is only something men are supposed to dare say?

One possible reason is that if a girl giggles at every joke like she's supposed to, it means she's not really getting the punchlines but doing something to please the man who is entertaining her. Which, yes, does signal passivity.

I should mention that I'm not endorsing this universe.