With GPS its not so much the location but thr change in time commitment. The new location is never 5 min from the preious but 30-45 min difference. People in these groups often have busy lives so if your 3hrs suddenly becomes 4hrs its simply less of a headache to cut the unnecessary thing rather than change 50 other things in your schedule. Eventually this scheduking effect shakes off all thr people in the group with other time commitments.