Curiosity Killed the Cat
Or, in this case, a Kim, a Park, and the original housekeeper and her husband.
If the Kim family doesn't sneak down the subterranean stairs, there's a chance their scheme is never discovered (at least not until Kevin's friend Min comes back) and they get back to their apartment before all hell breaks loose.
Sometimes minding your own business is the best thing you can do.
Food in Films: Before watching this, I had no idea what ram-don noodles were. Now I can't stop thinking about them and their delicious noodly, beefy goodness. Kudos to Mrs. Park for a bravura eating performance!