Because someone thought it was interesting, and enough other people upvoted it.

It’s been posted many times, I think mostly due to it’s association to Mitchell Hashimoto. It’s left as an exercise the reader to determine why this is important.

Looking at the comments it seems like there are still people not using it

Just because you know about it doesn’t mean others can’t benefit from the mention.

https://xkcd.com/1053/