DasYochid…
The point you are missing is that primary elections are to elect delegates to the national political party conventions. While you may cast your primary vote for X, you are not voting for X. You are instructing your state party political convention to appoint/elect delegates to the national convention who pledge to vote for X on the first ballot.
Since state party rules vary, as do state election laws, the federal government doesn’t get to set rules for primary elections. Sometimes, the state supporters of a particular candidate don’t gather enough petition signatures to get X on the ballot. The federal government can’t tell states how many signatures are necessary.
The primary elections are state affairs, no federal official is being elected, in fact, no public office is being decided.
The states’ rights in this matter are sovereign under the 10th Amendment.
The fact that is doesn’t seem logical is not the issue.
MAYBE….if we ever amend the US Constitution to have direct election of the President, then we could have a primary process under federal rules.
Remember, you and no other elector has ever cast a vote in November for a candidate for US President. We vote for a members of the Electoral College tp be named later that will vote for the President. This is why we can end up with a President who lost the popular vote. The will of the poeple does not decide the Presidency in the USA.