It was stated in the github issue discussion that part of the reason was to support the STEEM price by shifting more rewards to power up. I agree with you that with 13 week power down, this is simply annoying and has negligible real effect, if not counterproductive.

I'd personally like to see no required power up on author rewards. Set the default at the current 50% or 20% or something and let people change this as an account setting according to their own preferences. Users and authors should not be pressured or forced to be investors if they don't want to be.