The burn mechanism is an important failsafe mechanism that allows Splinterlands to die and be reborn again. Card and collection values are in my view more important than the DEC Peg, if the game is in a state where everyone is leaving and selling (like it is now) it gets the prices so low that people who want out have to burn their cards and dump the DEC below peg. This reduces the card supply which is needed to make them more attractive again.
Removing this mechanic would mean Splinterlands would likely die with no chance for it to be reborn unless some other card burn mechanic is invented.