Logic and usecase for remote subfolders

Not a special reason, it could be handy when accessing the remote files using a file browser instead of the Duplicati software. For example, if you want to download the files to/from local storage for migration to another backend, of for disaster recovery tasks.
Apart from that, it just gives a cleaner look.

The filenames contain 32 random characters, because it’s a standard GUID.
But all characters (except the 13th) are random, so the filenames could be truncated to save some space in the local DB. I don’t have a clue how how much the db size would decrease because of shoreter filenames.