Going a little Abelson&Sussman, the utility of cons persists because it is a powerful abstraction. Fitting into registers was, as a scholastic might say, an as accidental feature as the input line voltage of a toaster [110 @ 60Hz makes things easier in this part of the world but isn't intrinsic to making crisp English muffins].

cons is useful for dealing with linked memory structures, including singlely linked lists and particularly singly linked lists where the stored value in each list element is a pointer because it abstracts over all the pointers. Writing code to process and manipulate and pass pointers is idiomatic in C. Using pointers is idiomatic Lisp.

Your barfing code shows why cdr and car persist. They are also powerful abstractions due to their rules of combination and probably because their rules of combination aren't constrained by a bias toward English language. There ain't no synonyms for "caddr" and "cdddr" in English or Python.

The idea that lists should be everywhere replaced by structs is assembly in any language thinking (also known as C). Lists provide a standard interface. Each struct definition creates a new data type.

It is better to have 100 functions operate on one data structure than 10 functions on 10 data structures. Alan J. Perlis, Epigram 9.