Gambling should never be considered a legit business. IMO casinos et al. should be shut down, for the same reason that payday lenders should be beaten to death in the streets: they’re fundamentally predatory businesses.
The problem with prostitution and organized crime is that it’s not victimless once the mob gets involved. “Bitch better have my money” is a threat; you pay the pimp, or you get beaten, and possibly killed. You want to hire an independent escort? I’m fine with that. But significant amounts of prostitution involve sex trafficking, esp. “agencies” that constantly advertise “new girls”.
All of the businesses that the mob–or any organized criminal gang–is in end up increasing costs due to corruption, and involve the threat of violence if anyone disrupts their money. People that try to compete in sectors controlled by criminal groups tend to end up dead very, very quickly, regardless of what the nature of the business is.