No, of course they're not necessary. They could turn off all their computers and then they wouldn't need any address space at all. But there are benefits to hav

No, of course they're not necessary. They could turn off all their computers and then they wouldn't need any address space at all. But there are benefits to having networked computers, and there are benefits to doing that networking correctly and not paying the costs of NAT and overlapped address space. It would take them years to renumber off of their /8, at great cost and with the result of an increased ongoing operational cost, and for what benefit? That /8 would last the public internet for less than a month. It's not like the people who are yet to deploy v6 are suffering a lack of time, so buying them an extra month which they would then squander isn't going to be very helpful.