It depends what you want to show, in this case I was showing the size difference between a file unencrypted and encrypted. An all-zeros file has nearly no randomness, so it compressed very well. Then I show that somehow the encryption process takes away this lack of randomness, and leaves a file almost incompressible. I'm really just increasing the scale to make it more 'dramatic'.

If I happened to be showing how compressed codecs like jpeg, mp3 or h264 weren't compressible, I would definitely pick something more like an actual text file.