Quite apart from not wishing to commit such scenes to my memory, there is the aspect that they WANT you to watch them. They are filming them because they want you to be repulsed, shocked, scared. I'd rather not give them want they want.
For a very short time in the mid nineties there was a video tape you could purchase, that featured quite a number of executions in various guises. A mate managed to get a copy before the video was blacklisted and taken off the shelves. Curiosity got the better of me and I watched some of the video. I was cured from that moment at wanting to see another human being lose their life in the manner that I witnessed.