trees in golden rock
Cost is the main reason from what I've always heard.
And probably a lot of rock.
A lot of our roads have no shoulders. Poles stuck in the ground inches from the road. They'd have to trench the road to lay lines. I'm should that cost is way more than a pole every 100 ft or so. Then you have pad mounted transformers to put in. Probably more expensive than the pole mounted units. They rust too. Maybe more so than the ones on the poles.