Imagine a raffle where tickets cost $1. After the winner is drawn, the house agrees to buy back the first few losing tickets for $0.99, the next few for $0.98, and so on until they work down to $0. The players don't stand to lose everything in a moment, but it's still pretty clearly gambling.
In (spot) market movements, your value goes down as the market declines, but you don't stand to lose everything in a moment.