Yes but that's not the reason. Back in the 90's shareware scene long before Github, an overwhelming number of files would be downloaded to your computer and then you'd be left to wonder where to start. Making a file all caps draws your attention to it and lets you know where the author intends you to start. Today, Github opens that file for you on the front page of every repo, so it doesn't matter so much anymore.

Yes. And even with lowercase, when all you have is ASCII, all caps becomes a reliable/x-platform way to add emphasis. The question is a fun watercooler topic but the accepted answer is among the various reasons the convention arose - it probably doesn't have a simple answer that's The Answer.