Beyond that, does anyone really look at it as anything beyond a solution for v4 address shortages? It's never even been a consideration from anyone I've spoken to that v6 supports something "we need", except for larger addressing possibilities.
I suspect the excitement in wheel reinventing may have allowed v6 to lose sight of doing something neat, like remaining compatible with v4, and allowing full adoption of ATM everywhere.
The "good bits" of v6 have mostly been rolled back into IPv4. For example IPSec, Link locals, Mobile IP have all been backported to IPv4 from the IPv6 specification with varying degrees of success. This is why they have weird limitations, because they were originally designed with v6 in mind. Mobile IP doesn't work because no v4 stack supports it properly, yet it's a requirement to be able say your stack supports IPv6. Also IPv6 doesn't have "IP options" as such, so you don't get your traffic filtered by ignorant middle boxes. IPSec doesn't interact nicely with NAT[1] because nobody ever considered that you'd need to NAT IPv6. Link locals work better with v6 because v6 is designed with interfaces having multiple addresses on an interface in mind, where as v4 has one IP per Interface. I'm sure there are other examples around that can be given of technologies that were originally developed for v6 and were deemed useful so they were backported to v4 even tho they didn't "fit" quite as nicely. ---- [1]: Yes, I know there are work arounds for this.