It used to be (sort of)
You can ask the U.S. Congress why they did away with single ballot, multiple candidate voting via the 12th Amendment to the U.S. Constitution in 1804.
Prior to that point, the Constitution required the following for presidential elections:
The Electors shall meet in their respective States, and vote by Ballot for two Persons ... they shall make a List of all the Persons voted for, and of the Number of Votes for each; ... The Person having the greatest Number of Votes shall be the President ... In every Case, after the Choice of the President, the Person having the greatest Number of Votes of the Electors shall be the Vice President. (Article II, Section 1, Clause 3)
While this isn't all-candidate approval voting (you can't vote for everyone you like), it does share the very valuable attribute with vanilla approval voting that a vote for one candidate is not necessarily a vote against another, mitigating the spoiler effect. It can be considered a hybrid of approval and plurality.
The objections based on metrics such as majority preference, etc. are a little bit cherry picked. As noted, it is impossible to satisfy every conceivable metric as "optimal" using a single voting strategy or any combination of strategies. Approval voting maximizes voter satisfaction more so than almost any other method
A fundamental problem of voting is that popularity is at odds with preference. Approval voting sides with popularity over intensity of preference, wherein a candidate or position that is favored even slightly by a large number of people is given more weight than a candidate or position that fewer people intensely want to win. Other methods purport to honor preference or ranking among candidates, but are more prone to the spoiler effect due to weaker respect for the tolerability of a choice (plurality offers no respect for approval beyond one's "top" choice, which means second-best and worst are treated equally).
Range voting is a compromise between these extremes that retains considerable versatility.
As with every method we have seen before, it comes with a tradeoff--Do you want your most liked candidate to win, so badly that you are willing to pit perfectionistic tendencies against each other and throw the race to the mediocre coalition with the greatest solidarity, or do you want to arrive at consensus about which candidate the greatest number of people think is tolerable? You can't have both.
And of course some methods just outright forfeit information on both preference and popularity, and are easy to manipulate and game, which is the problem we are trying to solve.
Given that the original Constitution's voting system yields sizeable benefits we expect from Approval Voting, by reducing spoilers and eliminating partisan polarization on single tickets, I think investigating the rationales of the Congressmen who did away with it would be a worthwhile inquiry.