In a filesystem based database, you are locked in to whatever storage system is used. ODBC can provide access to other programs, but often has serious shortcomings in what it will allow you to do.
Web-based databases provide data in a predictable, standardized format that can be interpreted and used by any other program in any way. Putting data into a web-based system is similarly standardized. Any program can properly format and submit data to the application, provided it has proper credentials.