I think:

1. that’s the joke
2. this is just a watchface template, not an actual file being updated constantly

No it’s used for all types of data transfer and real time data as well.

I mean, I’ve never used JSONs before but I imagine you could still write to them in realtime at least, as inefficient as that sounds lol. So you could probably get the same results on an actual text editor if you could modify it to update the text automatically when it detects a change instead of prompting the user

API calls often return json. It’s just a data format.

/sys/: am I some kind of joke to you?

To be fair you won’t find Jason there. But plenty of files that provide real time information about the system!