"Usually weight savings is why a thin barrel is used"
True, but consider the opposite. A .22 rifle could probably be made with a barrel about the diameter of a quarter inch tube, and that would be strong enough. But would such a rifle be as handy and useful as a heavier one? A gun needs some mass both to resist recoil and to have good handling properties. One of the criticisms of the old Winchester shotguns with fiber glass wrapped barrels was that they were too light - what Winchester considered a benefit turned out to be a drawback.