High and Low Voltage Overhead Cable

on the contrary, those conductors are insulated by air as they go from point to point and with large ceramic stand off insulators where they pass a pole.

If they have to pass these HV conductors under ground they build an insulated wireway, much like wires in a house, but made for very high voltage

I would only add that for safety concerns, low voltage overhead wires are insulated because they are typically at a much lower height, where contact with tree branches, structures, and/or accidental contact with other things (people pruning trees, high antennas on vehicles, etc) is a real possibility. They are also typically much closer together.

There are additionally, code requirements that are based on the above concerns.

I would add:

Note

All cables are mounted on reasonably rated insulators irrespect of potential, insulated or bare conductors.

HV cables are on higher poles & on cross-members extending horizontally on pole sufficiently separated, while LV cables are also bare conductors but mounted vertically on pole. In localities which are densely populated insulated cables are used.

One thing to remember that insulated cables are costly, Temerature ratings low [same size in open air & insulated]

EHT are transmitted thru TOWERS not poles. so need not to insulate.

Another consideration is the ease of service in bare conductors.

Since no one has mentioned it yet I will. From one of my recent 11kV projects, one of the main reasons why overhead high voltage cables (around 11kV and above) are not insulated is that there is no point. The insulation suffers voltage breakdown issues unless it also includes a semi-conductive layer(s) also (simply to short out the capacitance created between the conductor and the air with the insulation acting as the dielectric, which the insulated HV cables incorporate). BUT, if you think these insulated cables are safe to touch you would be wrong (they are NOT). So, where does that leave us. Well you would need an insulated cable with a earthed copper or aluminium screen (a bit like a coax cable but a lot bigger). So, its either an inexpensive bare wire supported above where the average person is likely to gain access or, a large diameter, heavy, expensive cable that is (generally) safe to touch.

And that is why.

If you are being forced to use insulated cable, then perhaps you have tree-related issues next to your lines (HV lines and grounded trees = not good).