Well no, you're not monitoring all sites on the system. You may be scanning all of them, but RF only travels so far, and thus by trying to scan every site, you're going to hear less because the scanner is wasting time looking for activity on sites it can't possibly receive.
Program only the sites local to you, and try to limit it to one or two sites that you get the best reception on. If you're not hearing the GSP/TPK on West Orange, see if you can receive another nearby site that may carry those talkgroups more frequently.
But definitely stop scanning every site in the system, because that is very counterproductive.