What good reason to hang long cable carrying electric current high above the ground? Assume no flooding or other natural disasters to damage the cable if it is laid beneath the ground, then what good reason for them to be suspended high above the ground? The cables are insulated and only carry electrical current so if money is no problem then is there any good reason to keep them off the ground? I think the reason for the suspension is due to the fact that exposed cable can shock gravesrobbers accidentally since they didn't have more concrete back then but I suspect there is a sound scientific reason too, right?
 A: Going underground is more expensive then suspending in air in at least two ways.
Initially having to dig a trench or use a "mole" (which is less disruptive) and then when there is a need for a repair (identifying the fault and then access to it).
There is also the problem of dissipating the heat generated when the cables are carrying electrical power because cables have resistance.  In the air this is relatively simple because the cables do not have to have to be wrapped in an insulator and then surrounded by a conduit containing oil to prevent overheating.
A: As the OP points out, the damage from flooding and other natural disasters, as well as the costs are the reasons for placing the cables above the ground. If these didn't matter, placing them underground would be better than keeping them in the open air. Note that costs involve not only actually placing the cable udnerground, but also planning a route for it (which can be complicated in urban areas), as well as identifying the breakage points, performing repair and simply replacing old cables.
A: Several reasons, some of them more apparent than others
As you already pointed out: Damage from environmental conditions. Earthquakes and flooding are problems in many places around the world, and underground lines are exceedingly expensive to repair. The whole process of locating faults underground is time consuming, and they are not exactly just copper lines down there, but have complicated insulation requirements for field propagation reasons*.
Cost of initial construction Obviously, above ground high voltage lines are cheaper to construct, and much cheaper to upgrade.
Near field energy propagation As alluded to in the first point, electrical conductors do not exactly transmit power in the metal itself. Rather electrical power is transmitted through electromagnetic fields, and the conductor merely provides you a way of constraining the electric field into a neat tubes. All conducting materials near the wire also interfere with the electromagnetic field created, and constrain them. This robs you some of the power transmitted, at least in AC lines. You can think of this in terms of magnetic field saturation, or in terms of parasitic capacitance. Earth conducts electricity, especially when wet, and wires suspended above ground have better efficiency
A: The very long power cables are run at very high voltages to minimize resistive losses. They also radiate. Both are reasons for putting them up high.
