It's not really about whether or not IPv6 is simpler than IPv4, though. It's about how painful moving from IPv4 to IPv6 is. And it's very painful. If the only thing that changed between the two was that the IP address space is bigger, it would reduce the pain of changing.
I'm certainly not going to claim that my experience is representative of anyone except for me, but the reason that I'm not going to shift to IPv6 until I literally have no other choice is because doing so is an enormous undertaking. Since IPv6 doesn't bring me any benefit that I care about, there is no reason to do so unless I simply can't get on the internet without it anymore.
Please note: I am not bashing IPv6 here, and I'm not saying that a change isn't needed. I'm just expressing some of the reasons I've seen why people resist changing to it, and that I think adopting it would have happened within a reasonable timeframe if it weren't as ambitious.