Two, that disciples in the sects were not like average humans. They had more spiritual energy cultivated from their many years of training, lows being fifty or so years for beginners and highs being in the hundreds. Of course, the more spiritual energy an object had, the more time consuming it was to draw the years from them without their willing consent, but at least it was easier to steal from them than spending hours and hours taking all the spiritual energy from small plants.
