The tax on rewards is simply to benefit long term authors and stakers over short term authors and speculators. You get your tax back if you stay powered up. If you power up, opt for the "free" power down, IE the 13/4 week one, you'll still be gaining that passive ROI back with your HP. So you only hit the ones that instantly power down all of their rewards without ever keeping any powered up, which are the people that should pay the most. They don't get hit that hard. They get most of their rewards, and they get them quickly, a change most would still take over the current setup.