The 10th amendment says'

Amendment X
The powers not delegated to the United States by the Constitution, nor
prohibited by it to the states, are reserved to the states respectively, or to
the people.

For the same reason that "murder" is a state crime, "speeding" should be too.
The only federal crimes, according to the Constitution, are treason and
counterfeiting.
Some federal use the 14th amendment to expand federal powers in the aim of
insuring HUMAN rights but manatee have no constitutional rights.