That is really cool, Cider. You're into something that normally takes years to grasp or even care about: evaluation of lisp expressions.
My compliments.
There are some practical usages for that kind of processing. The most common application is appending to the startup function - as you can see examples of in the help for DEFUN-Q-LIST-SET.
But also if you wrote, say, a graphical calculator and wanted to create functions on the fly from user inputs, you would need to handle functions as lists and evaluate them on demand.
Besides the practical usages, playing around with quoted lists and evaluators such as EVAL (naturally) and LAMBDA is a doorway to greater understanding of how lisp works.