UABB Business Reviews module requires the Google Places API key to display reviews of Google Places and the same goes for the Yelp. This article will help clarify your query regarding why you can only display a specific number of Reviews in Google Places and Yelp.
Did you notice that you are unable to display not more than 5 Google reviews in this module?
Well, there are some challenges which make this process a bit complicated to display more than 5 reviews.
Firstly to be able to retrieve all the reviews for a given business is only supported if you are a verified business owner and it requires other requirements that only work once those criteria are passed.
Due to the complexity of the same, we are not including the same right now in our module, you can follow the steps which needs to be followed – https://issuetracker.google.com/issues/35825957#comment71
Here』s the reason for the Yelp reviews not returning more than 3 Yelp Reviews – https://www.yelp.com/developers/documentation/v3/business_reviews
If there are changes or it gets eased moving ahead in the future we will surely make changes accordingly in our module.