The update hinted that using more power then necessary is wasteful and makes you look sloppy and unrefined. We may still rise up in ranks by going all out but soul reapers take many precautions when in the human world to restrain their power and collateral damage. If we had no ambitions in the human world I would probably want us to go all out but we do want to be sent to the human world.This is a tournament. Exactly how many tournaments in shonen anime were about people showing off how cool headed and responsible they were rather than how skillful they were?