You have it backwards, if a new user has a lot of power already, then there would be no reason to purchase SteemPower. And if I lose my perks that I get when holding SP, when I may as well power down.

Also, if brand new account started out with some power, then the system would be subject to sybil attacks, as people would just create tons of accounts and you'd see way worse havok then anything you see now.