If the goal were to have a mutable list data structure, then switching to a backquote representation is a source code optimization which might or might not be p

If the goal were to have a mutable list data structure, then switching to a backquote representation is a source code optimization which might or might not be possible, based on what the list structure should be. The user then needs to find out if it is possible or not. That may cost additional time and may introduce errors.