It's a function of the language. If you're working a Lisp, association lists are very much the "default" for mappings, and the style of code built around them i

It's a function of the language. If you're working a Lisp, association lists are very much the "default" for mappings, and the style of code built around them is very clear as a result (in most lisp-like languages, at least). For example, there's no special constructor for an alist: you just create a list, which can be done using the lisp syntax itself. Whereas for something like a hash table, you likely have to call a constructor or something. It's all just a consequence of lisp's syntax and structure being largely built around list manipulation. In contrast, languages like Perl or Python have literals and syntax support for both lists and mapping-type data structures (hashes in Perl, dicts in Python), so using either one is roughly equally elegant, and you are more free to choose one or the other based on performance concerns.