Mamta B. from Google posted her first time in the Google My Business Help forum detailing a lot of the changes that is happening with the new Google+ Local pages, not just that they are removing reviews but more.

Mamta said the following features are no longer supported for Local pages; reviews, categories, directions, stars, photo uploads, interior photos, maps, hours, opentable/apps integration. That is a lot to remove, but Google+ is now about collections.

Here is the full FAQ she posted, just in case it changes:

Forum discussion at Google My Business Help.