Because now we get to have the other trope of "how did you know where that was?" that comes about when people are hiding that they're living together.Which begs the question why she would be dumb enough to offer up their common home as a study point. Go to the fast food/family restaurant like every other manga trope.
Pretending for others is a whole lot better than pretending to themselves that they're not in a real relationship, and it's only because of whatever crap pushed them together in the first place.Oh yes the annoying let's pretend we arnt married and don't know each other at school trope. How original and fun...