Domain Local group vs Global group

Hi,

I came accross this text on MS web site about using groups in AD

http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/ServerHelp/95107162-47eb-4891-832f-0c0b15b7c858.mspx

When to use groups with domain local scope
Groups with domain local scope help you define and manage access to resources within a single domain. These groups can have as their members:

• Groups with global scope
 
• Groups with universal scope
 
• Accounts
 
• Other groups with domain local scope
 
• A mixture of any of the above
 

For example, to give five users access to a particular printer, you could add all five user accounts in the printer permissions list. If, however, you later want to give the five users access to a new printer, you would again have to specify all five accounts in the permissions list for the new printer.

With a little planning, you can simplify this routine administrative task by creating a group with domain local scope and assigning it permission to access the printer. Put the five user accounts in a group with global scope and add this group to the group having domain local scope. When you want to give the five users access to a new printer, assign the group with domain local scope permission to access the new printer. All members of the group with global scope automatically receive access to the new printer.

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Why can't i just use a Gloabal group with five users and assign it Printer permissions.
It says i have to add the Global group to Domain local group and assign permissions on it.

thanks