Transmission towers and towers are usually made of steel. The use of high-quality conductors as load-bearing structures for high-voltage wiring seems counterintuitive. But "load bearing" is the problem.
Few materials can be used to build various high-voltage electrical towers and iron towers so that the high-voltage wires are high enough on the ground. Insulation materials are often too strong to break in the next high wind, or to be too pliable, to sway and bend very hard, or they are too expensive to build large structures.
Well-designed suspension insulators can support steel load-bearing parts, which is an excellent compromise between high cost and sufficient safety.
