Gambling and loansharking are hand-in-glove. A guy who can't afford to go to the track or a casino is likely not to have enough ready cash to bet at a level he wants but can't afford. The odds are not what makes Mob gambling operators rich--it's the vig on the loans. As for the borrowers: victim is as victim does.
Re. payday loans: Here in AZ, payday lenders are permitted to legally charge 15% per week, which works out to 496% compound annual interest. That's way more than Mob loansharks charge.