Good question.
No, that's not the reason. I always keep minimum 20% of pool balance liquid, so that should not happen easily.
The negative USD profit is due to DEC price drop. I have many cards that were purchased when dec was near the peg. Now I'm selling those cards at USD loss but still earning more DEC than what I payed initially.
For example:
1$ card would be 1000 dec at peg
And also 0.5$ would be 1000 dec when dec is half of it's peg
Oh woah... it is wild to track things that way. Incredible account practices!
These USD losses are mostly coming from pool accounts. Pool users are expecting profits in DEC, not USD, so I can sell the cards for USD loss as long as we get DEC profits.
For personal accounts, anyone can manually lower card prices, but not many people do. I also recently added a buyback mechanism that shares part of the profits with older/losing cards, so technically, all cards should sell eventually.