I do not believe this is the way Google Drive works. The app, if I am not mistaken, allows you to view (and edit some Google documents) but maintains them in the cloud. While it does allow you to download them, it saves them to your Download folder for local use only.
You can choose photos you've taken from your gallery and upload them to Google Drive, but (if I am not mistaken), there is no automatic folder syncing option.
You can use Google+ though. It automatically adds all your photos to a Google+ album only you can see. Given, not as easy as Drive, but still a good auto-upload option. I don't know of an easy way to get them from there to a Drive folder though :/
You can also use FolderSync. It could sync folders with Google
Docs, and still works after Docs upgraded to Drive, Google Drive is
fully supported. Just choose Google Docs when adding account in the
app. In case, you don't want to pay, its [free lite version][3 is also
in Play Store, but with some limitations.
Thanks for the above goes to Sachin Shekhar.