for some people they have more money than it is worth time and effort to remove the stuff.
i bought my civic with 2 12's, 2 amps, avic n1, stinger batts, polk components..
my girlfriend bought hers with 3 type r's, v12 amps, fiberglass enclosure, alpine dvd, type r comps. its a pain in the *** to try and sell all that shit.
guy who sold me my car was a pilot for continental and didnt give a shit, guy who sold my girlfriend her car worked at CC and got all the stuff cheap and already had a new system in his new car.