Scalping was done everywhere in the world for as long as there have been people. But it was Europeans who put bounties on Native Americans by offering money for their scalps. Usually an adult male's scalp was worth twice that of women and children scalps. The US government paid a bounty for it all the same.

So it's no wonder Native Americans retaliated by scalping white colonizers alive. You'd do the same if your family was murdered for less than the price of a horse.