Gambling is no different from any other consensual crime. Prohibiting it does not make it go away. It merely pushes it underground, where it is impossible to monitor for cheating and fraud, where the stakes are likely to be higher, and where problem gamblers stand to lose quite a bit more than merely their pay packet. When you make a popular activity illegal, you also create new sources of funding for career criminals. It is fairly well known that America's experiment with alcohol prohibition gave rise to the mob. But Al Capone and his rivals also brought in big money from the numbers racket.
Consensual crimes like gambling also produce no aggrieved victim to report or provide evidence of the crime. All parties to a sports wager or illegal card game participate willingly. So in order to enforce these laws, police must go out and search for criminal activity. This creates a number of problems.
Les Bernal's argument against gambling is near what you would expect.