These are just the rules of the community called "The Scene". Fitgirl is not scene, for example. Also torrent sites are not part of the scene. Groups which release their content to torrent sites are usually called P2P groups. Torrents have built in hash checking as part of the torrent protocol. A release is only "The Scene" if it is listed in a predb.

The reason that Scene use CRC32 is probably because the scene is focused on racing. SHA256 would have a much longer calculation time. The scene has bunches of different groups, but there is only allowed to be 1 scene release per content slot. The scene rules set a minimum quality requirement. Whichever group fills the slot first has their group name in the predb forever. If a release is a duplicate or doesn't match the rules, then it gets "nuked". The groups compete with each other to be fastest.

I think also the CRC rule was originally decided in 1998. This might be the main reason.

https://scenerules.org/html/1998_GAMEiSO.html (1998 scene game release rules)

In either case, be sure that you are not creating a solid archive, because if you do, the FTP sites will not be able to test the CRC integrity of each of the individual 15 meg segment file.

Before you start thinking about uploading your RAR files, please run a quick CRC test on each .0* file to check the validity of the archive. Ensure that you didn't run out of hard drive space during the archive processing which could result in bad files.

https://scenerules.org/html/2021_GAMEiSO.html (2021 scene game release rules)

1.15 The final release directory may contain only the following items:

• RAR archive volumes
• NFO file (singular)
• SFV file (singular)

https://en.wikipedia.org/wiki/Standard_(warez)

https://en.wikipedia.org/wiki/Simple_file_verification