It's just a standardized file format, and a bunch of legacy traditions that once served a purpose and don't anymore. It really doesn't make a lot of sense to package a low budget short film in a disposable milspec travel case.
Here's what you actually need. A shock resistant thumb drive, some bubble wrap, and that festivals exact requested digital encode format. You can probably just take your print, run it through Adobe Media Encoder or similar, and conform it to the requested format.
It may sound complicated, but this is really just "format your video file to their specs, and put it on a thumb drive and mail it"
I carry expensive equipment in pelican cases, but there is no need whatsoever to package a short film on a modern thumbdrive like that.