You are correct that - for many common environments - IPv6 lacks a compelling case for deployment. However, that is not universally true: for those organizations closer to the core of the Internet (with corresponding larger traffic and growth rates), the premise that you can carry all the traffic through CGNAT fails (simply review communications on the nanog mailing list from organizations such as Comcast, T-mobile, ATT, Google, MSFT Azure, Amazon, Verizon, etc.) to see clear evidence of such…. IPv6 solves their IPv4 exhaustion problem and has allowed the Internet continue to grow - if you’re not seeing a similar need, then it is simply that you are not at the core of the Internet.