Good question. Consider this as one possible answer: casino bets or sports bets are "all or nothing bets."
When you bet $5 on an positive expectation video poker game you hope to either hit a winner or you will lose all $5.
When you bet $5 on a share of stock you also hope to hit a winner, but you have a chance to bail out either at the same price, or a slightly lower price, or at a much lower price. For example, you buy at $5 and sell at $4. Is there a similar casino bet that works this way? (Do sports bets work this way when a game or season is in progress?)