In the house? They just don't. They're kept warm enough by the general house temps. We don't put pipes of any kind in the ceiling or outside walls.
Our water well, Rog keeps a 100W light bulb down the well area, and it's covered, and keeps it just warm enough to keep it from freezing. Occasionally, water mains will freeze and burst in the cities and towns, but it's actually quite rare... all the water lines and sewage lines are buried deeper than the frost goes down.
People in mobile homes have to keep an eye on things, generally, but the skirtings need to be insulated and a heat source, often people will wrap the pipes with a heat tape... You grow up with it so just learn how to manage the cold. Vehicles have a block heater that gets plugged in to keep the engine "warm" - really just so it will start. The radiators have antifreeze in them...