Briefly: an election only counts if everybody can believe the results. Making an expert level understanding of CS a requirement to verify your voting system means that Joe Q. Average who doesn't hold a PhD (or maybe even a college degree) has to rely on spooky experts telling him what to believe. If I were in his shoes then I would have no confidence that I participated in a fair and valid election.
We kind of live in a bubble here on HN where most people are sort of in the tech space and could take a weekend or two to understand blockchain. I think its easy to forget that most people don't have the required background to learn it easily (or would want to use up their time to understand it). I almost have a PhD in the hard sciences and I don't fully understand the finer details of block chain. I think I would have to write my own implementation to fully appreciate it.
Simplicity and the ability to explain the system to every American is a requirement of any voting system.