I looked this up recently and was surprised to see that the first of these was posted just few days ago.. (I was expecting this to be at least a few months old)

As per knowYourMeme,

the original instance of the series was uploaded by artist Garnet Hertz via his Facebook page on February 2nd, 2012.

Source: http://knowyourmeme.com/memes/wh…

I guess some of the reasons this became an internet rage:

  • Realistic and Humorous (Most of the times): Focuses on mundane realities of life (most jobs are not as shiny as they seem to be). while allowing  you to laugh at others and self: Self-deprecating humor is usually popular.
  • Virality factor: Most people can either relate directly to the post. In other cases, after seeing one of these posts, people think of how this would fit in their jobs. In first case, people would share; in latter, they may go ahead and design one that describes their job (See next point). In both cases, their action contributes to virality.
  • Easy to design: Unlike some other internet memes, you don't have to spend too much time drawing images or shooting videos. This even doesn't require too much thinking. Most of the time, you just have to do a think a bit about your job, and then do a quick Google image search for images that would fill the standard placeholders.

See question on Quora