Amazing. So, tell me, how does my software vendor enable "32bit syscall emulation" on my IPv6 stack to use my IPv4 address there? They can't. There is no way to do it.
Please be serious. I didn't have to touch a thing to use my old 32-bit software on 64-bit or 32-bit Linux/Windows/whatever on amd64. This was done by software upgrades (or not even that if I stayed on 32-bit OS) and other automatic means. Red Hat, Apple, Microsoft etc. did this for me and everyone else.
In contrast, if I want to have currently useless IPv6 connectivity, I have to get an address (or more than one), reconfigure my DNS, my firewalls, my services etc. And now multiply this by a few billion and you'll get the amount of effort required for IPv6 setup around the world. Then, I have to maintain these two in parallel for some time to come. Oh, and this is just so I get to the exactly same functionality I have right now on IPv4. And, I'm going to make a whole heap of mistakes in the process (it's a new thing), which will cause a whole heap of unforeseen problem on my networks.