That never made sense to me. The only time it does, IMO, is in the middle of a shooting war. Trading the Soviet spy for Powers was more than worthwhile, given the risks Powers took for Uncle Sam every time he zipped up his flight suit and the working-over he absorbed at the hands of his Soviet interrogators.
Eisenhower had ordered the U-2 flights stopped, to avoid any incident which might imperil his impending trip to the USSR (where he would address the Russian people directly in a speech, among other things).
But the CIA went ahead with the flights anyway.
(Hey, since when did a President have control over the CIA?)
There are even suspicions that the plane was set-up, in order to scuttle the Ike trip.
He knew the risks. We traded an asset more important than FGP. Why didn’t he destroy the aircraft? When time came for him to perform he failed.