That's why it says "should be" instead of "are." You can click the title to read the article.

The current system wasn't intended by the founders either; they wanted us to select electors, representing Independent candidates, who could then vote their conscience. The Tenth Amendment, however, allows states to change anything the Constitution doesn't talk about — which means they can bind electors or allocate them proportionally. They can't, however, opt out of having electors.

This system was ingenious back when traveling to your state's capitol would take weeks; if a candidate died, or if a scandal erupted right after the election, electors could just vote for someone else. Today, though, it's quite outdated — and the founders knew this time would come, which is why they allowed for constitutional amendments.

What I propose doesn't need an amendment, since states can just choose X electors from one party and X electors from another, but it would be ideal, since it would change the system nation-wide and prevent inconsistencies.