Vito would have never allowed that because it could have implications down the road and effect Tom's stature as a lawyer.
Exactly, DC! And, under Michael's Donship, he needed Tom to be "legit" and "clean" to represent the family in Nevada and advance Michael's quest for "legitimacy." We tend to think of Tom's being "out" as consigliere as a punishment for not being a "wartime consigliere...things could get rough." In fact, he needed to be unconnected to the rough stuff so he could be untainted when he represented the family at gaming license hearings, etc.
