As a corollary - maintenance of buried power lines is more expensive due to all the digging which has to be done. Power line inspection is also trickier. I als

As a corollary - maintenance of buried power lines is more expensive due to all the digging which has to be done. Power line inspection is also trickier. I also wonder if the unions representing linemen have a strong influence on "bury" vs "overhead" since most of lineman's job involves work up a pole rather than a tunnel. Lastly - burying anything in the ground in areas where the ground has been known to move (California is the "Earthquake" entry in the Bingo game of "choose which natural disaster" that is the continental USA) is liable to be a non-trivial endeavour, one which will require ongoing inspections and the like.