Because many users/services have only IPv4, practically all services and ISP have to provide IPv4 and do not have to provide IPv6. If we could agree to kill IPv4 at specific date, we could have truly IPv6 Internet years ago.
User should not use IP addresses. This is what we have DNS and mDNS for. In special cases, like local router if mDNS is unavailable, IPv6 address is even easier than IPv4 (compare "FE80::1" to "192.168.0.1").
Anyway, it's not like it's a choice unless you want to restrict who deserves public IP and who doesn't, because we do not have enough IPv4 for everyone.
Most average users don't notice IP addresses and would have no idea if their system is using IPv4 or IPv6 in ordinary day-to-day life, so long as it works. Statistically it's average home users that are already using IPv6-first if not IPv6-only and ISP/Carrier-Grade NAT6TO4 (most mobile networks, and a plurality of home networks), where it's increasingly Enterprises and certain types of power users holding on to IPv4 addresses that seem to be the biggest hold outs on IPv6.
Because many users/services have only IPv4, practically all services and ISP have to provide IPv4 and do not have to provide IPv6. If we could agree to kill IPv4 at specific date, we could have truly IPv6 Internet years ago.