>>538315357
Firstly, she's kinda the "fail safe option" if you don't spring for the others (or can't get Rins route to trigger) but not disinterested enough to trigger the manly picnic.

Secondly the main way to trigger her route is to follow all the directions the nurse gives you. And since Hisao makes a big deal (rightfuly so) about how bad his heart condition is, new players will tend to follow his orders, because that's what the rational person would do in his shoes after having a heart attack and arithmya diagnosis at such a young age.