Serious answer, because in order for federal law to supersede state law they have to make their own law that "occupies the field" [1] or explicitly says in the

Serious answer, because in order for federal law to supersede state law they have to make their own law that "occupies the field" [1] or explicitly says in the law that it preempts state law. [1] https://www.law.cornell.edu/wex/occupy_the_field https://www.law.cornell.edu/wex/occupy_the_field