It's still related to copyright law. If the law promotes, say by making it a default, that one side can easily benefit from a certain behaviour, then people, c

It's still related to copyright law. If the law promotes, say by making it a default, that one side can easily benefit from a certain behaviour, then people, companies will assume that as the behaviour to favour. And then these are the consequences: that going around claiming rights on whatever you feel like is not only not punished by Youtube but carelessly accepted. Because it's just easier, less effort.