The mob threatens, kills or maims people for failure to pay. They have no other enforcement mechanism. This negatively affects entire communities, or even major cities, regardless of whether or not you see it.
I doubt you can find much statistical evidence of casino legalization lowering the murder rate in cities.
The mob still lends money when legal casinos open...
How many addicts who only use the legal gambling wind up killing themselves or damaging their bodies via substance abuse, after being bled dry financially?