""Can someone remind us again why the Internet Engineering Task Force decided not to make this next-gen networking protocol backward-compatible?""
Presumably because that would have been massively restrictive, and have meant lots of legacy baggage?
The move to IPv6 might be very slow, but it is starting to happen - and will likely accelerate with the widespread use of IoT - and the exhaustion of IPv4 addresses. Companies like Colt had an IPv6 backbone network several years ago...
IPv6 is at least partly backwards compatible in terms of you can easily gateway most IP traffic from one format to the other.
Biting the hand that feeds IT
