Lack of interest Prompt Mobile Users to bookmark

On the forums I manage, 30-35% of visits come from phones (more if you include tablets). Since we don't support native apps for iOS or Android, it would make sense to bolster user engagement by encouraging users to create homescreen shortcuts. I have seen this on websites for Android (CBS, below) as well as on iOS. It is simply a prompt for the customer to interact with their browser's chrome/buttons.

Does this exist?


Do other forums (e.g. see such a substantial mobile presence? Would this be considered as part of the core forum?