I can totally understand why. IP addresses are hard to get for a large chunk of the global population. There's twice as many people as there are IP addresses.

Plus dual-stack means more work, and more possibilities for misconfigurations or vulnerabilities in your network. It'd be way easier if you only had to worry about one or the other.

I live in the US and my ISP gives me one address I have to share across all the machines in my house. That's a tragedy - by all rights I should have a subnet or two. You can't directly address any of my servers from the outside on IPv4 which means I have to do hacky crap like port forwarding and can't use a lot of the older protocols that aren't NAT friendly. And I've got it good compared to most of the world!

IPv6 gives us back a large chunk of the original premise of the Internet - that all nodes are peers. IPv4 hasn't been able to do that for decades, and it's warped the way we think about networking by separating everyone into consumers and providers.