How can you say that gamblers are attempting to get the money of others? How do you define the word "others" there, is it the people? other gamblers? Either of that two is not correct.

Gambling sites or even casinos has their own capitals on the start. That means, they have their own money that they can use to give the people the prices or their winnings. The money there doesn't circulate as to gambler to gambler, that stops at the owner most of the time. Also, the owner pays tax to the government so some of that money is being paid to the government. Gambling is not wrong but if you are getting greedy because of it, that is wrong.