The two sites are separate from each other hence why it's not gamegrep.neoseeker.com and which is also why you have to log in twice. It's the same as GFXcess, DEVNPEN (which actually uses a different forum), etc. Unfortunately it's not something simple to implement. Implementation might involve some methods that may not be so secure for your personal information (username, passwords being stored, etc) and as such was not included as a feature when GG was launched.