Yes businesses tend to only work on interoperability when the interoperable product is just a complement to their main revenue generator. Like how Netflix releases clients for many platforms. No one is going to be motivated to make a (1) free (2) easy to use (3) cross platform file sharing solution. It'll also draw the ire of the copyright cartel. File locker websites have been harassed and "legitimate" cloud storage services are forced to police their user's files.