Art is all about making interesting things that serve no functional purpose, though often they have useful byproducts.

This is a work of art.

One use case of something similar is generating a regular expression matcher at compile time for example. This is what the C++ library https://github.com/hanickadot/compile-time-regular-expressio... does.

There are a lot of uses of compile-time code. One I have been interested in is generating bindings to other languages or generating serialization code, or even generating bytecodes for VMs with specific bytecodes for accessing your native data structures (instead of adding a level of indirection).