Question : Backing up an Exchange server

Hi,
When you backup exchange with ntbackup I read that you need to create two seperate backups for your system states and your information store. Personally I do not understand why, can anyone explain why this might be the case?
Thanks

Answer : Backing up an Exchange server

Backup operation fails when you back up Exchange Server 2003 databases and System State Information at the same time

http://support.microsoft.com/kb/820272