Earlier quoted context omitted.
I'm not sure they aren't. All of my Google+ photos wound up in Google Photos without any work on my part, other than maybe actually accessing photos.google.com.
Isn't it funny that we're even having this conversation? That Google can offer two products, differentiated by a single character (Google+ Photos and Google Photos), with few obvious indicators as to which I should use? It's confusing to me, but trying to explain it to my mom is absolutely impossible. I wonder whether the average user even knows there's a difference between the two. It's a perfect example of unnecess…
Look at the Inbox vs Gmail experiment for example. While not tied to Google+, Inbox runs parallel to Gmail and accesses the same things. Just a different window dressing. I'm sure many at Google want to see Inbox take over Gmail at some point.
This is one of the reasons I doubt we ever see a Material Design Gmail. I think they'll run with it until Inbox is "ready".