IPv6’s addressing scheme provides more addresses than there are grains of sand on earth — some have calculated that it could be as high as 1030 addresses per person (compare that number to the fact that there are 1028 atoms in a human body!). With IPv6, it is much simpler for an IoT device to obtain a global IP address, which enables efficient peer-to-peer communication.
The importance of IP to the Internet of Things does not automatically mean that non-IP networks are useless. It just means that non-IP networks require a gateway to reach the Internet.