I am sorry to say this but its the truth, the reason why you might never win big money in gambling is because of the mentality you have before entering into the game. How can you already conclude writing you even before a game that you would lose?? Thats very wrong and this way, theres no effort you put into it that you win.
Those you see risking large amounts of money do so because they are sure it will come back, even though it doesnt at times, it is normal and it definitely would come back again some other time, life is all about risk and risking so much in gambling to win triple the amount invested is a risk all gamblers must take.
That's not about his mentality or whatever you called it. He was only can afford to lose that amount so he only bet with small amount. There is nothing wrong about that, sometimes when you think you would lose, you will ended up with big profit which unexpected thing from gambling.
Whales who betting with huge amount, they are either want to rich quickly, can afford that amount or just playing for fun. How can you be sure 100% your money which you have spent will come back to you? This is not charity