Why does the S3 ActiveStorage service force binary encoding?

In activestorage/lib/active_storage/service/s3_service.rb, whenever Rails downloads files from S3, it also runs .force_encoding(Encoding::BINARY). Does anyone know why?

This seems to be part of the original implementation for Active Storage (Rails 5.2). Binary encoding can also be understood as “a valid but unknown encoding”, which is appropriate for a service that is supposed to be able to handle any type of file, but originally was basically supposed to be used for images, compressed files, docs, excel, etc.