In a domestic environment, each house in the row is connected to one phase in turn. Over a street-full of houses, it probably balances out. Where I live, in a little group of 5 houses, I've no idea how it works! But I guess that averaged across the village, it's OK.

What you should avoid (I'm pretty sure that there are regulations about this) is having two or more different phases available within reach of each other. Not quite sure what the minimum spacing is, but the idea is to avoid anyone connecting themselves across these two phases which will be even more likely to kill than just phase and earth/neutral. Obviously, that doesn't apply when all three phases are being used together, but in that case they all go to the same appliance/tool/whatever.

Kettle sounds like a useful find - I have to walk all the way indoors from the garage to make my coffee!