Other mistake: In the opening scene where Moneypenny is holding the rifle, you can see the flash suppressor was installed upside down. The 'slots' are on the bottom. (00:10:35)
Other mistake: During the chase through the London Underground station, in the shot before Silva jumps onto the escalator, a female extra can be seen looking directly into the camera. (01:31:40)
Other mistake: When Bond is being driven back to MI6, there is clear rain on the window. In the angle from above the car, there is no rain visible on the top of the car, meaning that there is rain on the passenger window, but no rain on the car roof. (00:26:45)
Other mistake: When M is attacked by Silva during the parliamentary committee's hearing, Silva enters the room from M's back and M turns 180° around her own axis to face Silva - now M's own desk is at her back, that is, her very own desk cannot and is not protecting her from Silva. A few seconds later, after the gun battle intensifies, her desk is now located between herself and Silva, and she is using the desk as a protective shield against Silva's bullets. (01:40:45 - 01:41:20)
Answer: Because Bond is fighting to the death with a man who's trying to throw him off a train. He can't exactly step out of the way.
Brian Katcher