It's not being burnt, there are two useful things we're doing with the 64-bit network size: * Sparse networks. 64 bits is too big to feasibly do a brute force

It's not being burnt, there are two useful things we're doing with the 64-bit network size: * Sparse networks. 64 bits is too big to feasibly do a brute force scan on, which reduces how often servers get exploited by random network attacks. * SEND secures NDP by using those 64 bits for a public key Reducing network sizes to 12 bits would destroy both advantages.