Gmail attachments need to have their own life. You should be able to forward scattered attachments. If you don't need an attachment, you should delete it, without deleting the entire mail. Attachments should be searchable, as they provide much more context to an email.

Yahoo Mail tries to implement separate views for attachments and the result is impressive. Maybe Google decided to wait until GDrive's launch. </img> </img> </img> </img>