Well, not just cakes are stored in these; sometimes rolls, cookies, or rotisserie chickens. Also the joke is that we care it’s loud because then we have announced that we are eating late at night. Sometimes this wakes people, and sometimes you just want to snack and not have a conversation, or at the very least be polite to people sleeping. Same with the microwave beeping three times loudly when you heated something up.

Also, “big cakes in the fridge?” implies that cakes are sold and stored by the slice. They are, but they also come in wedged shaped boxes made from this plastic. Also it is usually leftovers, like there was a whole cake, but now it’s a third of a cake left on some weird slippery cardboard tray. You had a party, most of the cake was eaten by others, but you didn’t want to waste the last bit. It takes up a lot of room, is fragile, and spoils quickly. But your significant other is on the couch sleeping off a hangover, so being quiet is considerate.