They actually do that, perhaps not for everyone but for new customers. For example Verizon made IPv6 mandatory when introduced LTE. A lot of people not realize

They actually do that, perhaps not for everyone but for new customers. For example Verizon made IPv6 mandatory when introduced LTE. A lot of people not realize they even use IPv6. The sites which are IPv4 only are going through CGNAT. The article says there's 10% adoption, but that's for the whole world, US currently has 25% now.