They're allocating /64s because a lot of the design of IPv6 (SLAAC, for instance) makes it easy to do one /64 per customer who would have been doing IPv4 NAT. A

They're allocating /64s because a lot of the design of IPv6 (SLAAC, for instance) makes it easy to do one /64 per customer who would have been doing IPv4 NAT. And the rest of the world bakes assumptions around this; for instance, IPv6 spam blacklists generally operate at /64 granularity because that's assumed to be one customer, so if customers get anything smaller like /96s or even /128s, unrelated customers will share spam reputation. In a world where we kept the IPv4 worldview of NATs and just added more addresses, a 64-address space would be fine for the same reasons that /64s are fine in IPv6 today. And the holdup on IPv6 rollout isn't related to it being a longer address space at all.