I would argue that's not really a good thing for online service delivery. It feels heavy-handed to do a retina scan if I'm trying to vote. I would argue that each of these things needs to be used.... We need to look at the spectrum of services and then the level of assurance. Not all of these things are in the same kind of category.
For low-level assurance services, we don't need as much trust, so getting to that higher level is not as important. What's also important about the retina scan and the NEXUS card is that it's done in a controlled environment. I have to go to a controlled kiosk with people watching me so they can see if I'm tampering with the machine or mucking about with the card. It's that controlled environment that gives them the confidence to do it that way. You couldn't do a retina scan from home, as an example, with any kind of confidence, because it could be a replay attack.