DOC file type association with Office 2007 - Why does it not happen automatically?

DOC file type association with Office 2007 - Why does it not happen automatically?

I have Windows Vista machine and I recently installed Office 2007 (I did not have earlier installations of any office product). The installation was a complete success with no error messages etc., however the association of DOC files with Office 2007 is not setup automatically. I have completed it manually now and it is working fine. My question is