Trees must have plenty of rooting space to be healthy and structurally strong. Don't use barriers to seal your tree in a tiny pot. Most tree root problems are the result of tree-illiterate landscape and structural designs. Valuable trees are damaged and removed every day when roots are invited into areas by design and then grow into problems. The tree, in this case, is only doing what comes naturally.
Root barriers are great tools to prevent tree-root colonization and damage.
In the end, they protect the trees and your home, and all the other places where you don't want roots to grow.