Being able to stream a collections of bytes (and collections of collections of bytes, recursively) is one case that I find myself wanting when sending data between programs at the command line.

Consider:

  ls "$pid_directory" | xargs rm

If there were some way to encode items in a collection OOB, you could pipe data through programs while getting some guarantees about it being represented correctly in the recipient program. (Sometimes you see scripts that do this by separating data in a stream with NUL delimiters, but this doesn't work recursively or if your main data stream might have NUL in it.)