Google+ Profiles are now not needed for posting a review on the Google Play Store. Until now, Google used Google+ profile to allow users to review an app on Play Store.
There are many users that use Google+ including techies, Google employees, preteens, and people with niche interests. Well, Google has removed the +1 Buttons slightly from all the users. Also, as per the source, the users without social network profile were able to write one or more reviews.
Currently, some users may need Google+ profiles but in near future they might not see any Google+ integration.