Think of it like phone numbers. For decades people have accepted gradual phone number prefix additions. I remember in rural Ireland my parents got an extra digit in the late 70s, two more in the 90s, and it was conceptually easy. It didn't change how phones work, turn your phone into a party line or introduce letters or special characters into the rotary dial, or allow you to skip consecutive similar digits.

For people who deal with ip addresses, the switch from ipv4 to ipv6 means moving from 4 digits (1.2.3.4) to this:

   2001:0db8:0000:0000:0008:0800:200c:417a
   2001:db8:0:0:8:800:200c:417a
   2001:db8::8:800:200c:417a

Yes, the ipv6 examples are all the same address. This is horrible. Worse than MAC addresses because it doesn't even follow a standard length and has fancy (read: complex) rules for shortening.

Plus switching completely to ipv6 overnight means throwing away all your current knowledge of how to secure your home network. For lazy people, ipv4 NAT "accidentally" provides firewall-like features because none of your home ipv4 addresses are public. People are immediately afraid of ipv6 in the home and now they need to know about firewalls. With ipv4, firewalls were simple enough. "My network starts with 192.168, the Internet doesn't". You need to learn unlearn NAT and port forwarding and realise that with already routable ipv6 addresses you just need a firewall with default deny, and then add rules that "unlock" traffic on specific ports to specific addresses. Of course more complexity gets in the way... devices use "Privacy Extensions" and change their addresses, so making firewall rules work long-term, you should use the device's MAC Address. Christ on a bike.

I totally see why people open this bag of crazy shit and say to themselves "maybe next time I buy a new router I'll do this, but right now I have a home with 4 phones, 3 TVs, 2 consoles, security cameras, and some god damn kitchen appliances that want to talk to home connect or something". Personally, I try to avoid fucking with the network as much as possible to avoid the wrath of my wife (her voice "Why are you breaking shit for ideological reasons? What was broken? What new amazing thing can I do after this?").