Ask HN: What concept do you wish was already a XKCD comic?

I've found that when explaining complex concepts to colleagues, nothing works quite as well as a good XKCD comic. Randall Munroe has a unique talent for distilling intricate ideas into simple, humorous, and highly relatable panels. It's amazing how often an XKCD comic can illuminate a concept, making it immediately understandable.

However, I occasionally find myself searching for a comic on a specific topic, only to realize that it doesn't exist. This got me thinking: what concepts out there are still in need of the XKCD treatment?