They are communication satellites. Their orbits are selected for optimal communication, not surveillance. Collection of photo-intelligence is not part of their mission and would require large apertures for high resolution (if you want that). Another subsystem is extra complexity, extra volume, extra weight, extra power, extra processing, reduced system throughput, reduced system reliability, and MORE expense (per satellite, and fewer launched on a single booster).

What you wouldn't do is know much about satellites. You don't do navigation with cameras. You use GPS and maybe star sensors and horizon sensors.