The importance of user-provided reviews is skyrocketing.
Native apps also depend heavily on user reviews, both to determine the relevance of the app and to increase the quality of those apps. Most importantly, an app with a number of good user reviews is validated in the mind of a potential user, and can encourage them to download the app.
For that reason, it pays to request reviews for your app. Let your customers know that they can help you out, and make their app experience better overall, by leaving a review for your app in the App Store and Google Play.
A final word here. It’s totally fine to encourage positive reviews, in fact you should do so. However, do not demand high reviews in return for a deal or promotion. It doesn’t work, and it will likely cause issues for you in the app stores and among your customers.