It is because you can be lucky for a short time. And it shows that you just don't play enough. In the long run (i.e. playing everyday for a year) your deposit would go negative.
And the problem with gambling leader boards is that they aren't showing complete picture but rather present you these 'luck spikes' people had.
Yes, you are right, but I was just saying that not
everyone lose, at least one or two persons must win something (I think it would be statistically impossible that everyone lost). About the leaderboards, certainly some people there are just casual gamblers (in fact, usually half of the people in the weekly caesars leaderboard are fresh accounts), but the other half are (probably) everyday gamblers (and their profit sometimes fluctuates weirdly).