This one seems pretty obvious to those of us around computers and BBS and FTP in the nineties. On a side note, I made the pinky-thumb phone gesture to my 10 year old daughter a few days ago, and she didn't have a clue... Nor does she understand how my music collection plays without the internet. She just assumes my hacker skills have reached such level of Zen nirvana actual internet access is just a trifling detail and not a requirement.
I actually didn't see the answer I was looking for in there: command line/file system environments used to be all caps and there WERE NO lowercase letters for a long time. I remember when MS-DOS (whatever version) first began using/allowed lowercase filenames and it was like stepping into the future
"Historically it wasn't possible to make lowercase `readme` files" doesn't explain why, after transitioning to systems which allowed separate case in file names, `README` files remained uppercase while most other text files now have lowercase names.