Different gambling activities have different chances attached to them and when I mean chances I am referring to the probability you have for actually win the bet or hit the jackpot in games like crash and slots. This is basically because sometimes unrealistic bets can sometimes play out as a win and some other times bets that have a high winning chance can eventually become the losing bet.
That's why it called 'Gambling". You're not supposed to know which will come through, just make a rough guess, with the help of tool at your disposal and that's it... If it pays, it pays. I'm very emphatic about slot games as there are no formulas, strategies whatsoever to win major.
however some prefer to go for the big game with big odds and smaller winning chances.
Those set of games are called the underdogs. The reason most prefer them over the favourites would simply be that they generate a heavier win if it's their lucky day. Some believe in staking on the underdogs althrough, without getting bothered about how much they've lost -- they believe they'll surely recover all of it in a single win.