progress seems throttled because companies still want to charge for IPs and don't want to address that there is no IP starvation in IPv6 (yet).
TL/DR: ISPs have a valid reason to charge from IP addressing. The reason behind slow adaptation is money, but profiting of the IP address charges is a tiny minuscule factor in the equation.
As long as there's no direct access to the internet from each and every building, we will need a middleman to arrange for it. Consider that every building in developed world has access to the national power grid, but even that's managed by a middleman. The middleman needs to maintain the equipment etc., pay for employees and create profit for owners. It's only natural that the middleman requests a compensation for services rendered.
Although IPv6 address space is ginormous, it still has to be regulated if only to prevent addressing conflicts. We have already an infrastructure and processes in place that allow for regulation. Again middlemen who need funding to maintain the infrastructure, pay their personnel etc. - compensations of services rendered.
Adopting IPv6 is easy for a home user or a middle-sized company. Not so for large multinationals, governments, military organizations, financial operations, healthcare... or even ISPs. It's not a one-night or even one-year operation. It requires careful planning and step-by-step implementation with monitoring periods and very fast fallback capabilities.
Network equipment doesn't get thrown out and replaced just because there's a new model in the market, it's used as long as it works and serves the purpose. Outdated equipment that doesn't support IPv6 must be replaced. Mid-nineties 80% of the commercial infrastructure was running on custom applications written on Cobol - an insurance company database server doesn't get updated either as long as it serves its purpose, so a great many lines of code needs to be written or systems replaced, which requires again testing and monitoring periods. Personnel needs to be trained, maybe new personnel hired. And so on.
The public sector funded by tax money has on top of all that its very own, separate stumbling blocks on the way with politics entering the picture.
This just from the top of my head for some perspective. We're talking about huge financial investments, and that is, as usual, the real bottleneck.