Apparently there were several idiots heading each of the states who made their decisions.
As tracks moved from being 440 yards to 400m across the country a decision had to be made.
The NCAA decided to change their championship from a mile to 1500m in 1976.
They kept the mile for indoors as the other events went to meters.
The IAAF keeps official records for the 1500m and the mile. There is no official record for the 1600m.
So, yes, it's stupid to have a 1600m event ever established.
This is what was done as tracks changed:
100y, became 100m, the Olympic event
220y, became 200m, the Olympic event
440y, became 400m, the Olympic event
880y, became 800m, the Olympic event
The mile, became 1600m, not an Olympic event nor an official distance of any kind
Like I said, the mile remains an official distance for record purposes today
So each state the holds a 1600m championship had some idiot that made the final decision and now they won't change it for traditional reasons I guess. Which makes no sense because the 1600m history isn't that old.