Google has started displaying the stars along with the reviews in the local knowledge panel. It is on the test mode now as not everyone or every business can see this.
This is considered to be a sensible step as a user can see the rating over the knowledge panel itself. They do not have to open the review section to check how much star an individual has given to that business.
Tweet By Tom Waddington (First One To Notice Change)
I assume displaying stars will make reviews more useful and stand out. On a regular basis, Google is trying to enhance the search result page with more and more features. Some business might get offended by this feature as fewer stars gives a negative impact on the new customer.
Source: Technians News