The material design team at Google gives a clear definition of what settings in your Android app should do:

App settings let users indicate preferences for how an app should behave. They at Google also state that your users should navigate to the app settings either from the side navigation or toolbar menu—with an item labeled Settings.

Including settings in your app gives your users the power to control some functionalities of your app. This makes your users happy instead of angry—because they are now in control of how the app behaves.

It's highly recommended access to app settings. This will provide a better user experience for your users, which leads to a better review on the Google Play store, which then eventually gives rise to a higher number of app downloads (which boost revenue).

These are source files for the Envato Tuts+ tutorial: How to Code a Settings Screen in an Android App

Available on Tuts+. Teaching skills to millions worldwide.