If gambling is legal but using violence against debtors is illegal then the legal casinos out-compete the illegal ones but cut you off when the banks won't extend you any more credit instead of giving you a loan with a lien against your kneecaps, and the money goes to companies that aren't using it to fund the expansion of protection rackets etc.

If gambling is illegal then the profits go to organized crime and they don't follow any of the other laws either.