For a Lisp fan, merely learning another language is fine. It's the need to actually use that other language day to day that creates a lot of obvious wasted repetitive effort and friction. Without macros, much of what the software industry produces is essentially macro expansions done by hand (sometimes called "plumbing" or "infrastructure").
Hy was originally a project to show "Hey, see how awesome Python & AST is!". Lisp being an easy choice to implement. Just awesome it have turned into something actually use able and fun to code with.
One use for such a thing I can think of is to use it as a reference for teaching basic parsing techniques. E.g. have a project for an undergrad course where they learn how traditional recursive descent parsing works, and then they get to implement an s-expression parser (possibly to a simplified version of the python AST).