Power supply in USA & England

[Colly0410]

Here in England just about all low voltage power supply lines in urban & suburban areas are underground & use a big multi mega watts 3 phase transformer supplying from tens to hundreds of houses, each house is connected to one of the phases & neutral giving 240 volts at each socket/light fitting. Only in rural areas & in small villages (usually) is the supply overhead... When I was in the USA in most of the urban & suburban areas the low voltage supply was overhead lines with small pole mounted transformers feeding 1 or 2 houses, only the newest housing developments were supplied by underground lines. Anyone know why there's a difference?