Because bits are not expensive anymore, and if we used 64 bits, we might run out faster than the time needed to convert to a new standard. (After all, IPv4 is still around 26 years after IPv6 was drafted.) Also see the other notes about how networks get segmented in non-optimal ways. It’s a good thing to not have to worry about address space when designing your network.
This is because NSA has two roles: eavesdropping on foreign adversaries, and protecting our internal systems from adversaries. Under the first role, they might introduce an exploit known only to themselves. Under the second, they help protect US systems from exploits known to others.