They do so in low earth orbit, ~500 miles. Out at 22,000 miles it isn’t so easy to track those objects.
NASA and the DoD cooperate and share responsibilities for characterizing the satellite (including orbital debris) environment. DoD’s Space Surveillance Network tracks discrete objects as small as 2 inches (5 centimeters) in diameter in low Earth orbit and about 1 yard (1 meter) in geosynchronous orbit. Currently, about 15,000 officially cataloged objects are still in orbit. The total number of tracked objects exceeds 21,000. Using special ground-based sensors and inspections of returned satellite surfaces, NASA statistically determines the extent of the population for objects less than 4 inches (10 centimeters) in diameter.
http://www.nasa.gov/mission_pages/station/news/orbital_debris.html
I'm still assuming that something the size of a football field is larger than 1 yard.