The 26th amendment was created so no citizen of the United States, who is older than 18 years of age, should be denied the right to vote.
The key word to this sentence is “right.” The 26th amendment was given to citizens as a right, not an obligation like taxes. It is the citizen’s choice to vote.
By automatically casting a ballot in the citizen’s favor would offset the politics for many reasons. Those who vote are the voices heard by the government.
A major flaw is that every “one percenter” who doesn’t vote will automatically be a Republican ballot, and the rest of the adults who don’t vote will be Democratic ballots. This sounds like an awful way for the Democratic party to have an upper hand.
Eventually that “best interest” will be manipulated to give more power to the government. Those who vote will get their opinions out there, and those who didn’t will complain about the government.