Well I don't think that downloading cias from games you dont own is legal either but here we are xD
they are 2 different things.
not everyone plays games they dont own. They hack their system for other benefits (such as backing up saves, having all your games on 1 sd card ratehr than multiple, custom themes, etc)
i only hacked my 3ds after the PKMN glitch that made your save unloadable when saving in a certain town...as it made me lose my only shot at event torchic and the blazenite.
Nintendo bricking a device you own is damaging another persons stuff and would get them sued and they would 100% lose as you OWN it. not them and anything you decide to do to your device is your business (hence why they only ban consoles and dnt make code to brick them when discovered to be hacked)