most of the Scrum terms work in the same way, used to describe different pieces of work, seperating them into smaller manageable pieces based on the time frame it takes to complete each piece. Why? Its all about motivation theory and the relationship between motivation and time, essentially its all about how to make the team more productive by creating a sense of urgency. This is also the main purpose of Stand-ups and Time boxing.
Believe it or not, these motivational strategies make me want to work less hard, not harder. They reduce my respect for the manager, and make me not want to follow them.