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.
Oddly enough, when downloading a file using http or https the file gets corrupted when interruptions occur and do not reliably resume the downloads. Needs a complete deletion and restart.
Too, although I am not an expert at it, I am informed that using an ftp service is the least-demanding useage of system resources one can find, thus its continued popularity.