Not every process can, or should be automated.
1) Impossible automation: Nothing can ever be completely, 100 percent automated to the point where it can handle every single scenario thrown at it. As Julian posits, "any computational device — computer, brain, anthill, whatever — can run into problems that it can never solve.... In practical terms, this means that every process, not matter how well automated, is likely to encounter conditions that it can’t resolve by itself: errors and exceptions." So, every process, no matter how brilliantly and elegantly executed, will break somewhere along the line, and require human intervention.
2) Unaffordable automation: Some things will take far too much time to change and automate than worth it.
3) Irrational humans: The subtitle says it all. Julian drives the point home, noting that pilotless passenger planes and driverless cars are technically possible, but no one is going to sign over complete control to these vehicles. "Humans are awful at taking rational risks, and happily demand a sense of control in preference to actual control."
The third point may be the most significant of all. Automation is great up to a point, but then there is a chasm of trust in systems and machines that many managers and executives find difficult to leap. Just as employees and business partners need to earn trust over an extended period, so do the machines.