For operating system APIs, it would be lovely if we could assume the shiny happy situation where all data is encoded correctly, and all encoding declarations are correct. Unfortunately, it just isn't true, and we took the position (in PEP 383) that it was better to ensure code like the following worked properly even if there was improperly encoded metadata in the filesystem:
all_stats = [os.stat(name) for name in os.listdir(dirname)]