"We cannot issue an IPv4 address to each machine without blowing out the cost of the subscription. We cannot use IPv6-only as that means some of the internet cannot reach the VM over the web."

This "some of the internet" must be significant

What about HN commenters who think IPv6 use by mobile carrier networks is a justication for others to use it

According to this blog, there is more to the internet than mobile carrier networks and other IPv6 users