In large part, because of ISPs. There are big costs to the transition that none of their clients care about. Besides, NAT gives ISPs insight into their users (

In large part, because of ISPs. There are big costs to the transition that none of their clients care about. Besides, NAT gives ISPs insight into their users (number of devices, services running on devices, how much traffic each service uses, etc). So you can probably do regional pricing based on that and some other things.