They discovered that having their mark on a product meant they could charge more for it. From there it was a short step to the first cases of imitation and trademark infringement. Brands, though, are now about much more than makers marks. Just look at some of the words used to describe them. Brands have personality, attitude and appeal.
Brands have awareness, reach, values and associations.
These are not qualities you can burn into a cows' hide with a piece of hot metal. That seems to make more sense. I've ever come across. I'm also making connections with every article I've ever read about Nike and third-world workers, and every pair of Nike trainers I've ever owned. That swoosh is suddenly conveying a whole lot of information.