OK!

Bittorrent, as you know needs ports other than 80 , and here, in most of the locations in my country they have closed most of the other porst and so using torrent is not feasible.
As you see in many posts using torrent has problems.

wget -c, ok! I said, FTP is much more limitted than HTTP. for example, the proxy server here is so that FTP resuming is not possible for us.

Generally HTTP is more popular than FTP and so better support is available for it.

now please tell me, why not sharing the file as a set of splitted , for example, rar files?