That explains things - in my experience I have seen money as the most conspicuous main barrier in the Northeast. Get above a certain threshold of wealth and even in sparse areas they go underground and poorer areas can get a bit more density than usual before being forced underground. A suburb with power lines is on the lower side of middle class. An urban area with power lines is practically a red flag for poverty for the two go together.

Reminds me of the joke about cancer risk and lowered IQs and power lines - the mechanism of the damage is insidious - it doesn't act through radiation but through lowered property values.