I think particularly in japan main reason for setting up power lines above the ground is because of their unstable climate. A huge number earthquakes makes it easy to damage underground power system, also making them more expensive for constant maintenance. So it’s more convenient for japan to make thing that way. In Russia recently we started bury our power lines blow ground for the sake of better city aesthetics and better longevity of such systems. Cause they gather ice on them in winter, which thorns them under heavy weight