This is how DEC was designed within the game. Everything had a static value in DEC, and it was based on the peg price of 1000 DEC = $1. You can view this when you trying to buy potions. The DEC for a potion is a static price, and that is how everything used to be until DEC rose way beyond this soft peg price.
The only mechanic in place to try to keep the price near the soft peg is that the DEC reward pool gets inflated whenever the DEC price is above $0.001. For instance, when the price was $0.01, the reward pool was actually inflated 10x the normal amount. That is why the rewards have been crazy lately, and also why when the price dropped below $0.01, the DEC rewards took a hit as well.