The effect is to reduce rewards on that payout. Which you should do if your opinion is that the rewards being paid out on that content are too high.
No need to read into it any more than that. It certainly isn't necessary for it to modify behavior to be worthwhile; the reduction in rewards, which certainly happens without needing to speculate, is enough. So no basis to say behavior is the goal. Reducing payout is the goal.
Why does anyone care if the "payout" is "reduced" ?
What positive effect does this manifest ?
Other payouts are increased, and those other ones are a better driver of Hive growth. Short term the reward pool is zero sum: Every milker or dumb payout costs every more-worthwhile payout some money. Long term the reward pool is positive sum: Rewards directed to the payouts which add the most value to Hive drive up the value of Hive and create even more reward payouts going forward.