Because everyone has the automatic right to an appeal - which is a good thing since past history has shown that they make so many mistakes by convicting and almost executing innocent people.

Gary Scheck and Peter Neufeld, two of OJ Simpson's lawyers, founded and run The Innocence Project, which you can read about here:

http://www.innocenceproject.org/

and here:

http://www.truthinjustice.org/ips.htm

To date, they have secured the release of dozens of death row inmates, wrongfully convicted of murder who were awaiting execution.