In a sense, this is like asking &quot;If Turing machines are so great, why do we keep needing new variants?&quot;<p>Lisps are lisps because to some degree they express a particular model for computation. What makes them seem more alike than the varieties of stack based system is that the first pass at a notation for ordering application (parenthesis) is recommended by its similarity to the mathematical notation for ordering application. In other words, languages modelled [more or less] on lambda-calculus look like &quot;a thing&quot; by the accident of similar notation, whereas languages modelled [more or less] on Turing machines don&#x27;t look like &quot;a thing&quot; by virtue of the diversity of notation.<p>In practice, this means that Scheme and Common Lisp and Clojure get lumped together while Forth and Cobol and C# don&#x27;t, even though there is as much variation between the execution model in the first group as the second.