A /48 means every possible MAC address can be assigned to have its own block of 65,536 /64 subnets. We haven't come close to exhausting the MAC address space an

A /48 means every possible MAC address can be assigned to have its own block of 65,536 /64 subnets. We haven't come close to exhausting the MAC address space and if we did we could do so 65,000 times and still not have actually needed more than 1 client per subnet. A /32 means an IPv4 worth (4 billion) of ISPs can have an IPv4 worth (4 billion) subnets assigned to customers. I've actually seen similar arguments that IPv6 addresses should actually have been made shorter based on how ridiculously scalable the number of subnets is. Personally I think it's the right pick - a 64 bit int covers the routed portion and a 2nd 64 bit int covers the subnet portion all with no "extra" bits to fiddle.