Mostly for labeling what goes where - i.e. which freezer drawers have what food, whose clothes (and what kind of clothes) go where, and so on.

It's probably not as useful if you live alone or with just a single other person and can agree about where to put stuff and remember these rules - but in a 4 person household things tend to get a bit unmanageable :-)

A good thing about the iron-on labels (besides marking childrens' clothes) is that they stick on the cheap-ass Ikea storage boxes (Dröna?) that are just fabric on top of cardboard.