I have a 64-bit computer, it can address up to 18.4 exabytes, but my computer only has 32GB, so I will never use the vast majority that address space. Am I "wasting" it?

You are using the addressing bits in the form of virtual memory. Right now. Unless you run a unikernel system, then in that case you could be right, but I doubt it.

Anyway, this is apples and oranges. IP addresses are hierarchical by design (so you have subnets of subnets of subnets of ...), memory addresses are flat for the most part, minus some x86 shenanigans.

Yes they are all "used" but you don't need them. We are not using 2^128 ip addresses in the world.

But we do need them! The last 64 bits of your IPv6 addresses are randomized for privacy purposes, it's either that or your MAC address is used for them. We may not be using those addresses simultaneously but they certainly are used.

Despite that, there still are plenty of empty spaces in IPv6, that's true. But they will still be used in the future should the opportunity arise. Any "wastage" is artificial, not a built-in deficiency of the protocol. Whereas if we restricted the space to 40 bits, there will be 24 bits wasted forever no matter how.