Pitchers Bat 9th

In NO-DH leagues why aren't you given the optuion of batting the pitcher anywhre in the lineup? Odds are you bat him 9th anyway but, just curious.
http://forum-365.strat-o-matic.com/archivesn/
http://forum-365.strat-o-matic.com/archivesn/viewtopic.php?f=12&t=204293