If it is a Rico Case and you plead guilty, you are admitting to the existence of the enterprise which is the crime family.
In some borgata's that was considered breaking a rule.
If you look at the West Side they killed that guy Lawrence Ricci, in the 90's because he wouldn't take a plea deal.
Which was a SIN, because he was later found not guilty at trial
Gotti Sr. on the other hand insisted that his guys fight every case like he did.