Are your poles made of wood?
Wooden power poles are a common feature in power distribution the world over, low in cost, lightweight, and strong they are an excellent means of supporting overhead power lines.
Traditional preservative treatment of wooden power poles imparts uniform protection along the length of the power pole but unfortunately the rate of attack from decaying organisms is anything but uniform.
At the ground line decay rates are very high and as every linesman knows this is the common point of electricity pole failure. High decay rates and maximum mechanical loading work in unison to break the pole usually in bad weather when you are at full stretch.
And this is a waste of treated wood as the rest of the pole deeper in the ground and above ground are usually still in excellent condition with many years of useful service life left.