Are different houses out of phase?
While 30 or 40 years ago it was common to get 3-phase power in many European countries, today as a rule you get one phase. If you get the R phase, your next door neighbor will get the S phase, and the person in the house next to that will get the T phase. Over hundreds of houses this more or less balances the three phases. 3-phase power is still available at an extra cost, but households hardly ever need it anymore. (I remember my mother had a Miele washing machine which ran on 3-phase power.)
Industrial customers often will have 3-phase power, either because they need lots of power, or they use machines which run on 3-phase power, like synchronous motors.
Overall the three phases coming from a 10kV transformer station will be fairly balanced, with only a small residual current through the neutral.