There are a number of possible reasons for this. Here are a few:
- It would require the government to go to some trouble and expense for something that would not happen often. The government would need to have procedures in place for such a choice and would need to spend time and money creating and practicing those procedures.
- One reason Canada abolished the death penalty was because of the idea that it is not the place of the state to take a person's life. This does not change simply because the person wants to be killed.
- It would set a precedent. If the state is willing to kill felons who wish to die, it should be willing to help other people who wish to die. This would get the state into the assisted suicide business.
- Finally, it is not the place of the criminal to pick his or her punishment. It is the place of society to decide what punishment a criminal deserves. Allowing the convict to choose his or her punishment would go against this idea.