With save the specific problem is that Mozilla guys wanted to move all save capability to local DB + download, and to never allow writes to arbitrary local file

With save the specific problem is that Mozilla guys wanted to move all save capability to local DB + download, and to never allow writes to arbitrary local files, treating it as a security issue, which obviously is a problem for any sort of web apps running locally. Google tried to standardize FileWriter API that never made it outside Chrome, then later dropped it due to aforementioned issue.