If for whatever reason you are still running legacy Google Suite apps on your mobile device, Google has announced that come 3rd of April, 2017, they will be shutting those legacy apps down. This includes apps for iOS and Android and will cover Google Drive, Docs, Sheets, and Slides.
For Android this includes Google Drive for Android (prior to version 2.4.311); Google Docs for Android (prior to version 1.6.292); Google Sheets for Android (prior to version 1.6.292); Google Slides for Android (prior to version 1.6.292). As for iOS, this will cover Google Drive for iOS (prior to version 4.16); Google Docs for iOS (prior to version 1.2016.12204); Google Sheets for iOS (prior to version 1.2016.12208); Google Slides for iOS (prior to version 1.2016.12203).
According to Google, “This month, users of these legacy versions will begin seeing the below prompts to upgrade. Please note that after March 1, some users with very old versions will be forced to upgrade when they receive the prompt. If you are using any of these unsupported versions, we encourage you to download and install the latest version of that mobile application.” Google also notes that this does not apply to the web versions of the software since these are typically updated automatically anyway.