Sorry for the noob question but do we have transformer outside of every house? I can't find mine..
Its used for long distances to convert low voltages(and high currents) to high volatges(low currents) and viceversa.
In a local area, all houses are close, so a transformer usually exist at a local area, and from there power is sent to the houses.
But some houses, or a group of houses have their own as well.