The answer is to protect them. Rats and other foraging animals have been known to climb palm trees and eat the seeds and shoots, causing damage to the tree which can often result in its death. The metal band creates a traction-less barrier that most rodents cannot cross.
The white paint is to help guard against insects. Usually, the paint's chemical base acts as an insecticide, and it also helps bugs to stand on out on the trunk, making them easy targets for birds and other predators. According to Ralph Backhaus, a professor of plant biology at Arizona State University, the white paint can also help prevent "bark burn," which is more important when the trees are young and sensitive to the sun's rays.
We agree that the paint and metal sometimes looks tacky, but at least there is a method to the madness. Palm trees are an expensive form of landscaping, one that townships want to protect. For what it's worth, the reflective white paint has also been known to help drivers see the trees at night.
[Photo: Will McGough]