If you expect to move that server, say to move to a new colo provider, do you get an IPv4 address there? If you have to pay extra each month for IPv4 and get IPv6 for free, do you pay?
Legacy desktops, there are these things like youtube, netflix, they eat huge amounts of bandwidth. As an ISP you don't want that through your carrier grade NAT boxes. Better try to get customers to use IPv6.
These days many web pages are insanely loaded with ads, trackers, etc. Lots of connections, again really bad for CGN.
Big CGN boxes are also really bad for geolocation. IPv6 is better for that.
There is also reason to believe that gaming behind carrier grade NAT is going to be pain.
Finally, if there was one group of products supporting IPv6 early on, it was operating systems. Even XP can do IPv6. Web browsers support IPv6 for a long time now. So as soon as the network provides IPv6, just about all desktops pick it up and start using it.
I think the holdouts will be webservers, which was the other thing listed in the parent post.
If "Internet of Things" takes off, those things will be IPv6. Then you can give an IP address to every thermostat, every light bulb, every fire sprinkler head, every shelf tag price readout (saw some LCD shelf tags at a Whole Foods near Houston), etc. Those things don't care if they can't talk to some legacy Web site.
Then, in twenty years, everything on IPv4 is some creaky obsolete thing...sort of like how we have Windows XP things around now that aren't being replaced for various good reasons.