IPv6 was designed in the early 90'ies where the internet looked very different - this was even before the web. Large scale changes were much easier to coordinat

IPv6 was designed in the early 90'ies where the internet looked very different - this was even before the web. Large scale changes were much easier to coordinate and roll out. I dont think the players at that time needed incentives beyond knowing that the upgrade solved the address space problem. The problems of adoption can be compared to the Python 3 debacle. When Python 3 was first planned, Python were mostly used by enthusiasts which would be quick to adopt a new version - even if it had a few minor incompatible changes. But when the release finally rolled out, Python had become much more popular and entrenched and widely used by business and scientists which were more reluctant to adopt breaking changes.