Cause in trading you are not depending on your luck to come it is on your skill unlike in gambling where you are just depending in luck.
If you are that skilled then trading is a sure way of earning and we know that it's a better way of making profit on bitcoins. But if you are sick enough and you got stressed already with what your trades then gambling is better to relief that feeling out of that stressful day that gives you headache everyday.
It just matter on what the person intends to do. If he loves to trade then he needs to stick with it. And there are people that are earning good amount with gambling so they are good to stick with it.
Sometime you should also enjoy gambling with some fun games, because you can make your stress away from circumstances you encountered from trading. If you lose big in gambling, it can be adjusted to minimal amount and only bet for fun and not exactly what you expected tovet profit from it, just think and enjoy the game you played because gambling is prone to losing rather than you are in trading. Trading only losses the profit if there's no exat knowledge from the market price, and no updates from the current price of the stocks you are having trades.