There could be several reasons why you'd want to download an older version of an app:
If the official App Store methods fail, some users turn to external software. Tools like or older versions of iTunes (12.6.3) —which still included the App Store—allow users to manage apps and download IPA files to their computers.
Digital archivists argue that software is culture. When apps update, the old designs are scrubbed from history. Unlike a film, which can be remastered while preserving the original, software is a "Ship of Theseus"—it changes constantly until nothing of the original remains.
