Not only a few earn money in gambling, you can never be unlucky the whole time except you always make things difficult by taking much risk and not practicing safe gambling.
There are different perceptive to gambling, for entertainment and those who desperately are in need of profits, once the mind is desperate for those win there will be extra push behind to facilitate winning each games which can bring more disaster and loses, at this point the gambler is prone to getting addicted and losing more than enough.
That's mostly the case in the present where many online casinos are opening. People tend to look at it because they want to make profits but do not even consider the risk they will be taking once they are inside.
Gambling should not be taken like a simple thing because this is real money we are talking about and once we get hooked to it or chase the losses for a long time, we might find ourselves unable to even feed for the day. I mean, there's a chance that a gambler would sacrifice his own budget once he sees that he might get back his losses but that is never always the case. Sometimes, we will lose more after losing so much. The system doesn't have pity on us, it will just keep on taking our money.