Powering up $HIVE increasing one's voting power in both governance issues along with distribution of the reward pool. The amount of Resource Credits one has available increases as one powers up $HIVE.
The power down time on Hive is 13 weeks. Each week, 1/13th of the total is delivered to one's wallet in the form of liquid $HIVE. A lengthy power down time is viewed by many as a security feature. Like with coins in the savings account, the ability to remove any HP in the event of a hack is impossible. The time allows one to reset his or her private keys.