Meh. You get a guaranteed complete copy of the file you want, even if the download is interrupted for some reason. Like your internet connection goes out -which also defeats your cloud file services. Speaking as someone who does not have internet access at all times, cloud-based services are not reliable enough for critical functions.
Multipart and parity files are in use across the Internet. Resuming a download is pretty standard anymore. FTP’s only real use anymore is for anonymous file distribution in the case of, say, drivers for hardware, etc.