Global group naming restructions

Why are NT4 Global groups restricted to 20 chars, yet Local groups can be as long as 256 chars?

When adding a group you will be asked to provide a group name. It must be unique to the domain or to the computer being administered. A global group name can contain up to 20 characters. It can also contain any uppercase or lowercase characters except the following:
" / \ [ ] : ; | = , + * ? < >
A local group name can contain up to 256 characters. It canalso contain any uppercase or lowercase characters except the backslash character (\).