Those people who tend to make mistakes are likely the people who does not understand the real risk of gambling IMO, hence even if they will not get scam, they will still likely to lose in the long run if they are not doing a responsible gambling.
Sometimes people are too lazy to read the rules of the gambling site where they register. They don't even want to know what the rules are for the bonuses they receive. That is why some of them do not think to look for forums or sites with reviews on the site where they want to register and play. This is also why such people lose so much of their money.
I rather prefer promotions like stake offers where we don't have to be a new customer and make bets simply like they offer double UFC winnings if your fighter wins by submission and the bonus they give is direct cash with no wagers needed.