So in this matter, Donnie retained certain rights, namely transportation!
The scale of United States Logistics is too large, losing the bootlegging business would be extremely difficult for United States Logistics.
Keeping the bootlegging transportation means securing a highly profitable business for United States Logistics.
Secondly, without any major American conglomerate willing to take over the bootlegging alliance, and while Donnie must divest from the bootlegging alliance, these Mafia families in America become the only ones capable of taking over this business.
However, these people certainly won't submit to others willingly; if someone were really appointed to take over, who knows if they would be eliminated the very next day?
Since one person isn't enough, it has to be a group.
So, organizing them into a separate alliance binds their interests together. Although there will be competition within, it's at least less than competing with a single family.
