I will add some argumentation I collected for a proposal to stop the burn, I didn't run in the end because of the development with the DAO taking ownership:

Advantages to burn:
Well, the obvious advantage is that the DAO has more income to cover its cost. There is however, another advantage that may not be that obvious. By having more DEC income, the DAO becomes less reliant on card/pack sales being the only income. This could open up the option to sell less cards or make them cheaper, both are a good thing for the overall ecosystem.

The ‘but burn is good’ argument:
We all know about the flywheel and we all know that if there is not enough DEC available, SPS needs to be burned to get more DEC. I personally don’t subscribe to the idea that burning SPS increases the price in the long term, it just shifts value from DEC to SPS. Burning DEC on the other hand technically increases the value of DEC, so why stop it? Because DEC not in circulation is not a price factor. Whether the DEC is burned or locked away in the DAO makes no difference.
Of course, as we all know, it won’t be locked away in the DAO forever. It is given to the team as payment, but these payments are now mandatory anyway. So either the DAO can put DEC into circulation or it needs to put something else into circulation, which would likely be more cards to get your DEC one way or another.
The (hopefully) killer argument:

Burning DEC may drive up the value of assets slightly in the short run, but cards will have to be bought to compensate for the loss of assets in the DAO. In the end the DAO will have to foot the bill for the DEC burned, which means we all pay for the privilege to burn our assets.