Keyword stuffing is a black hat ASO (app store optimization) technique where practitioners stuff important keywords to an app page’s content areas. It is used in Google Play because Google’s indexing algorithm gives credit to the usage of main keywords in category rankings. 

Black Hat ASO practitioners ignore the quality and readiness of app description and they prefer overusing important keywords instead. Google started to ban and remove the apps that app developers practice keyword stuffing so it is not that much easy anymore to use that technique without notice.