Satellites had an inherent limitation in the world of espionage, Annie Jacobsen explains (in Area 51) — they worked on fixed schedules:
This would forever negate any element of surprise. The average satellite took ninety minutes to circle the world, and overflight schedules were easily determined by analysts at NORAD. The ironically named Oxcart was an attack espionage vehicle: quick and versatile, nimble and shrewd, with overpasses that would be totally unpredictable to any enemy. But most of all, in terms of clear photographic intelligence, nothing could compete with what Oxcart was about to be able to deliver to the president: two-and-a-half-foot blocks of detail made clear by film frames shot from seventeen miles up.
Geosynchronous satellites?
Geosynchronous satellites would have struggled to see anything in the 1960s. It was the age of analog film.
I remember being amazed when I learned that the first spy satellites used film, which had to be sent back and developed. They were giant disposable cameras.
Valid point. Mentally I live in a world where satellites have always been able to read the year of a quarter on the sidewalk.