Can you back up your photos to Google Drive without using both Drive and Photos apps?

Recently I've made the transition to Google Drive and so I installed the Drive app on both my iPad and my Moto X phone and checked the auto syncing checkbox in the settings but neither of the devices synced anything to the Drive. I decided to try installing the Photos app beside it and after ticking the photo sync box there (in the Photos app), everything synced perfectly to the Drive. Does that mean I have to keep both the Photos and the Drive apps to simply sync the photos and videos from my camera? Can't I achieve this simply with the Drive app alone?

Everything else syncs fine without the Photos app. Any files I add on any device syncs with every other device. The only thing that does not work is auto backup of photos from my mobile devices unless I have Photos installed beside the Drive app.