[racket] first and rest etc. only work on proper lists

The list processing synonyms (first, rest, second etc.) are not
"exactly" identical to car ,cdr etc.

car, cdr etc. work on proper and improper lists, but first, rest etc.
only work on proper lists.

Is there some reason these synonyms can't be made identical to car,
cdr etc. so  they also work on improper lists.  For someone new to
lisp like languages, first and rest etc. seem to make your code so
much more readable.

Thanks,
Harry