Satellites do have such restrictions. While you may expect the angle to be higher than for an aircraft, a satellite will not be directly overhead most of the earth. You’re still limited by angle and shadow, as well as time and frequency. Unless the target is high enough priority to reposition the satellite, it will be an oblique angle at a predictable time. While that angle will on average be higher than an aircraft, the aircraft can find different angles, at different times, with as much frequency as you like.

Perhaps some things are more visible to an aircraft from the east than a satellite from the north, or perhaps the target has camouflage procedures at the known satellite schedule but an aircraft is more likely to catch them operating

The biggest issue with satellites is they are on a schedule. The soviets knew the schedule and would move things like trucks around when they knew it wasn’t overhead.

You might like this book: en.wikipedia.org/wiki/Deep_Black_(book) It goes into detail on the keyhole satellite program and such. He says he used publicly available info and so couldn’t be accused of violating classified restrictions.

Thanks. I’ll take a look for it. Not listed as an e-book at my library so I might have to look for a physical copy