I assume the denser the population, the more it makes economic sense to put power lines underground.

The particular problem though is wildfires and they're more slowly caught, and can become larger and more destructive, the further away they are from population.

San Diego (SDGE) has a plan to bury most lines in the next 50 years. I feel like this would happen faster if they were not beholden to shareholders (NYSE:SRE). Distribution and the charges associated with it are government aided monopolies... Should a publicly traded company have a gov granted monopoly?

As far as I can find, SDGE is only burying their distribution lines. Their 1900 miles of transmission lines (which often cut through flammable wilderness areas) will remain above ground.