What is the key consequence of a satellite being placed in a retrograde orbit?

It requires significantly more energy to achieve compared to prograde orbits

Retrograde orbits involve the satellite traveling from east to west, directly counter to the planet's natural rotation (which moves west to east). Because the satellite must overcome the existing rotational momentum of the planet as well as achieve the necessary orbital speed, the energy expenditure required for insertion into a retrograde path is substantially higher than for a prograde path. Although less common due to this energy penalty, retrograde orbits are intentionally used because they grant unique access to specific geographical regions or surveillance angles that are difficult to observe efficiently using the standard west-to-east prograde paths.