I think your perception of filesizes is slightly skewed; "nine or more digits" means roughly >=100MB. Disk images, software, and videos would be in that range, but probably not the average MP3 (100MB of 320k MP3 is over 40 minutes), and I don't think I've ever handled a "word processing document" more than a few dozen MB --- and even that would already be many hundreds of pages.

Of the files sitting on my desktop at the moment, which is not necessarily representative nor typical but covers a wide range of types (pdf, mp3, zip, exe, jpg, mp4, ...), slightly more than 10% are 10MB or more (8 digits), ~15% have 7 digits (1-9MB), and the rest are below 1MB (<= 6 digits).