[agency]

They're also the original and simplest persistent data structures https://en.wikipedia.org/wiki/Persistent_data_structure

[guerrilla]

What criteria do you use to judge those two properties?

[Nevermark]

Not sure about original.

But simplest: Address pairs are extremely simple, obviously. But they can implement anything.

Lists, structures, arrays, trees, arbitrarily complex multidimensional and irregular data types.

Using symbols as representational "links" they can even implement general (multi-, etc.) graphs. Which is everything.

But remove one of those addresses, and all you have left are linked series of addresses, ending with one element, or an end-of-series marker. That isn't general or very useful.

So address-pairs get the prize.