Pot Odds and Calling a Raise from the Big Blind

[blinde]

Hi. I'm having a conflict between my intuition and (lack of) knowledge of pot odds.

My understanding is that the pot odds for two higher cards (AKo) vs. two lower cards (27o) is about 1.7:1.

Assuming your opponent probably does not have any pair (e.g., everyone folds around to the button and he raises), why wouldn't it be automatic to call a 3xBB raise?

50/100 blinds, Button raises to 300, SB folds, BB action. Costs 200 to call for a pot of 450. That's 2.25:1 pot odds.

Why is this routinely folded, even with a 2xBB raise?