Unlike full neck braces, Dainese's neck protectors don't prevent your head from being jammed down between your shoulders or side-to-side movement, but rather prevent your next from flexing too far backwards and provide protection from impacts. Less protection than a brace for sure, but you're more likely to wear this kind of neck protection more of the time, meaning you're more likely to have this on when you need it.
All of this protection is incorporated into Dainese's high-end jackets or is available in component form. We've never actually figured out a practical application of a street-use armor jacket since we prefer our armor incorporated into our jackets and wear our back protectors separately, but it does illustrate the degree of protection that is offered.
Also, what's the deal with the guys that wear jackets like this without leather over them? They get the need for safety, but don't execute it fully? Of course, we'll never understand the need for an extended swingarm on an R1 either.