Revealing mistake: Near the end when Ace gets into his Cadillac, in the first shot facing the front of the car, there is a protective glass in front of Ace (the same width as the windshield) with the dashboard in between that glass and the windshield. Note the vertical edge of the glass is visible at the right side, and the rearview mirror's sticker on the windshield casts a shadow onto the second glass. During the stunt, the flames on the dashboard are between the glass shield and the windshield, keeping the actor safe from harm. (02:46:05)
Revealing mistake: At the beginning of the film where Robert De Niro gets into his car and it explodes, you can clearly see the cut where they have replaced him with a dummy. (00:00:50)
Revealing mistake: When Sharon Stone gets thrown out of Joe Pesci's club, you can see the pads on Stone's hands to break the impact of the fall.
Continuity mistake: When Joe Pesci is beaten and then buried - look at the blood on his chest. In one shot it is all over - the next it is just a smaller patch.
Continuity mistake: In the scene where Sharon Stone is talking to Joe Pesci about how De Niro had his guys beat up James Woods, there are 4 security monitors on the desk behind Sharon Stone. First, the top left monitor goes out. Next only the bottom right monitor is on. Then all four monitors are off. Finally, all four monitors are on again. (01:18:05 - 01:19:20)
Continuity mistake: When Joe Pesci and his brother are beaten at the end, Dominick is thrown in the pit and facing one direction, after Joe Pesci is beaten and thrown on top, Dominick is facing the opposite direction than he was originally. (02:48:30)
Continuity mistake: Towards the end of the movie, when they first kill Nicky's brother, Dominick, and they throw him in the pit, his full chest is covered in blood, but in the aerial shot it is clean with just the bloody face.
Visible crew/equipment: When Ginger obtains the deposit box's key after having rushed to Ace's house and goes to the bank to open the deposit box, a boom mic can be seen reflected on the bank's glass door.
Continuity mistake: After the very tense encounter between Ace and Nicky in the middle of the desert with De Niro watching Pesci leaving quickly, the distance between Ace and his car changes enormously in two different shots.
Answer: It's also possible that the "bosses" would be concerned that a rift between Nicky and Sam could bring public (police) attention to the criminal activities going on behind the scenes. These are, after all, two very egotistical individuals.