I imagine that by moving this to the backend you could guarantee (at compile time) that all Ajax calls on the client have an associated backend endpoint. This eliminates dead urls, and gives you more opportunities for code generation or IDE-style autocomplete when creating Htmx views.

Do this in a static functional language and your whole app will more “deterministically pure”.

So yes, it causes more work on backend but, given more tooling, it can provide more opportunities for less code written overall via code-generation (like how creating a model in Rails generates lots of helpers).