The thing about automation as it regards to economics is that it doesn't have to be anywhere near a complete solution to have a huge impact. You don't need factories full of fully self-sustained robots to cause massive underemployment.

If you can partially automate a task to the point where 1 person can do the work that 2 people used to do, you've potentially eliminated 50% of that job's market. People are somewhat adaptable, so some amount of this sort of change can be absorbed (and has historically been absorbed) as people retrain for other types of jobs, but we're quickly approaching a point where the changes brought upon by automation are going to outpace people's ability to adapt to the changes, IMO.