Toasting doesn't just give bread a browned flavor. If the bread is stale, it temporarily improves its texture by softening the starch granules. The granules loosened and expanded in baking and have been contracting ever since the bread left the oven, gradually stiffening it. When the heat of toasting brings the granules to the point of gelatinization, what moisture remains in the bread moves in and briefly softens them.
But what about that idea of toasting a person? Why do we call the act of dedicating a sip of an alcoholic beverage "toasting"?
It comes from the medieval practice of adding a bit of toasted bread to wine -- particularly to wine flavored with spices -- to improve its flavor. (Toasted bread was an important ingredient in medieval cookery; many sauces were based on it.)