The answer is simple. If you live on planet earth, yes, ADSBexchange.com could use a feeder at your location. The map may look like you see aircraft in your area, but the truth is you can’t see what you can’t see.
Detecting an aircraft at 30,000 ft. can be done from a hundred miles away, but lower flying aircraft require the feeder to be much closer. To detect aircraft with MLAT, we need a minimum of 4 feeders to receive data and the more receivers see it the better the MLAT accuracy. If an aircraft is low altitude, feeders may have to be within a few miles.