The trouble with IPv6 pitch was that there are a lot of additional features beyond "more address space". However, other solutions and workarounds were developed so that those features failed to become a selling point. You could get that with current IPv4 + other protocols.

There is enough deployment now that pushing an alternative will face the installed base. There is a lot of IPv6 deployment out there that isn't always visible and that will stick around for a while even if IPv8 gains traction.