Many organizations have built custom functionality in SharePoint to meet their specific business requirements. Custom functionality is typically hard coded to the version of SharePoint that the functionality has been developed for. When it comes time to migrate SharePoint environments to the latest version of SharePoint, the organization is held back due to the customized features created on their current version. The time and cost to redo these modifications are factors that hold the entire organization back from getting the benefits the latest SharePoint version offers.
Using AppForms , it is significantly faster to re-configure the custom coded functionality than it is to re-code it. You can quickly recreate the forms and business logic or custom web parts while continuing to work with the same data sources like lists or databases. Once your custom functionality is now migrated to AppForms, it will easily port to newer versions of SharePoint as AppForms is completely metadata driven. This is the same paradigm as older Excel spreadsheets seamlessly opening in the latest release of Excel.