RAR has internal file checking and redundancy that allows it to recover from a level of transmission errors. Some of the more clandestine ways pirate teams transfer things are by means that aren’t totally reliable, so this is very important. BitTorrent uploaders tend to take the file exactly as they get it, so there you go.
BitTorrent has more sophisticated ways of checking correctness than RAR, so it’s not really necessary. It’s just too much effort for uploaders to bother.
RAR has internal file checking and redundancy that allows it to recover from a level of transmission errors. Some of the more clandestine ways pirate teams transfer things are by means that aren’t totally reliable, so this is very important. BitTorrent uploaders tend to take the file exactly as they get it, so there you go.
BitTorrent has more sophisticated ways of checking correctness than RAR, so it’s not really necessary. It’s just too much effort for uploaders to bother.