- Operating systems, browsers, etc are not distributed systems. Their deployment procedure has no availability or liveness requirement. And they can be done asynchronously, at the discretion of the user. If you think about it, deployment for this type of software boils down to uploading build artifacts into a public folder.

- Most other massively deployed software is developed by a single organization that completely owns the pipe. Ethereum has multiple client teams that need to coordinate and rigorously test their specs.

- Any failure has potential to severely damage the reputation of Ethereum, and in turn a multi-billion dollar market.