We certainly could run Federal taxes through States (mandate states to assess and tax income, use the Feds only to investigate states, not investigate individu

We certainly could run Federal taxes through States (mandate states to assess and tax income, use the Feds only to investigate states, not investigate individuals), but that requires an attitude of anti-Federalism that is too pedantic for the average government official or citizen who only has headspace for or "government", and is opposed by the modern Federalists who favor a stronger union (intentional power, less civil war) over general independence and local control. anti-Federalists lose because the governments they build are structurally weaker than Federalist. Similar to how the extreme end of Anti-Federalism, "we don't need laws; everyone should just be nice" is a failed model for practical government.