@jasonkoebler and Reddit has a perverse incentive to turn a blind eye to this. The more content people scroll through, the more ads they show, and the more stuff they can sell back to google. It doesn't need to be good content. It just needs to be good enough that people put up with it.
It would be immensely simple for Twitter to stop the bot problem, or at least reduce it. But then the numbers on the graph would dip down further.