You're probably right, most people won't bother, but abusers trying to maximize their profits certainly will. Which means more voting influence and ultimately more rewards will go to those who game the system, and less to the typical or casual users who don't. There are already bot herders with thousands of accounts. It isn't hard to manage a few more.
BTW, splitting up SP does not hurt author rewards. SP has no influence on author rewards at all unless you self-vote, which can still be done easily by having all of the accounts vote for the posts.