each people have rules with himself
if you can control yourself gambling is not wrong, but im never see people can control himself to stop gambling,
So Gambling is wrongway
I think the simplest way to explain this is - If you win, it's right. If you lose, it's wrong

You just specified where does gambler goes, which is win and lose only.
So the simple explanation in this matter was that gambling is really a Wrong things anyway. Why?
It is because you are risking your capital on which things you are not sure that you are going to win 100%