IPv6 is unwieldy. The addresses are impossible to remember and hard to type. Most people don't need to do either of those things, but the people who manage systems do. There's also little incentive for consumers and businesses to switch. The only way it'll happen is if it's imposed by large network providers.

Where I see it being useful is for IoT devices, where you're never configuring them manually, and where they probably only need to speak to one endpoint.

For anything that involves manual setup, you're going to have to force me to use IPv6, because I just don't care. Voluntary adoption is a pointless endeavor.