Because let's just say for example you're a 9-year old or something and your parents give you a Switch for a special occasion like idk a birthday or for Christmas and you turn on your Switch for the first time and want to play a game and you want to experiment with your new console such as running Homebrew applications or using a game hack like SurfShark or something to make a game more enjoyable like in Pokemon but Nintendo says "no, you cannot do that" so they lock your console forever.
It's illegal for a company to do that.