Most likely it's to protect the tree from bark damage and furry creatures like rats and squirrels.
Rats and squirrels are detrimental on home landscapes in many ways, including eating crop vegetables, nuts, fruits and birdseed. Both will nest in attics, if given a chance, and will gnaw through wood and walls as well as wires, pipes, hoses and insulation.
Trees often provide access to the higher reaches of your home, and even when isolated in the landscape, their trunk still offer rats and squirrels a way to climb up into trees and destroy fruit and nut crops.
Wrapping sheet metal around trunks will discourage them from using trees to climb up to your roof and attic.
Squaring up face to face with a rodent or a pest is every homeowner’s worst nightmare. Besides the potential health implications, the pure fright of finding a critter around the house is enough for millions of households to call out a pest control professional. However, these services can often prove a costly short-term solution and re-infestation rates are often high.
Here are some tips for keeping your home pest free at Atticpestauthority.com.