Yeah, it's not a problem of Detroit not being efficiently run or led, it's just that their activity is limited to what Ivy said - bookmaking and loan sharking in select areas. As long as the body count stays low and no drugs get involved the feds have higher priorities than a few guys running some card or dice games on the weekend.

NYC has the manpower pool to draw from while these other areas simply do not. With all the busts in the last 30 years it's just not feasible for anyone to join the mob anymore and that's why the guys in it now are considered reckless and untrustworthy - they typically have nothing to lose and so join the mob.

I'm not saying Detroit doesn't exist or that they aren't efficiently led by a smart, veteran group of guys - I'm just saying that what is there is small and limited in scope, which is probably how they'd like it to stay.