The MobileView API was originally made for apps. Now that the Page Content Service is being used by the apps, MobileView's value is questionable given its maintenance cost.
It has been marked as deprecated in T210808. Of course deprecating should be done carefully - there may be other consumers of this API, but we should explore who they are and how we can get them using MCS.
Note: The MobileFormatter will continue to exist for MediaWiki mobile web views. The MobileView API actually has a lot of logic that is not shared by the MobileFormatter.
Problems with the API
- Older versions of the apps use it for main page
- Uses an API parameter names inconsistent with action=parse
- Has a mainpage parameter that doesn't do anything.
- Nobody is maintaining it any more.
As of June 2020, neither of the current app releases (iOS 6.6 and Android 2.7.50320) relies on MobileView directly. They are using the Page Content Service. Prior to these releases, the Android app was using the Mobile Content Service and the iOS app was using MobileView. Enough users will have to upgrade to Wikipedia for iOS 6.6 or newer before MobileView can be removed (T236731).
The other element blocking removal of MobileView was incomplete language variant support in Parsoid (T43716). The Page Content Service used Parsoid for most wikis but needed to use the MobileView API for Chinese Wikipedia. Since T43716 was stalled, the Page Content Service was updated to remove dependence on MobileView for zhwiki and use the action=parse API (see T236733 for more information)