> It takes a brave interview candidate to say "the best solution depends on the exact nature of the problem - and your problem doesn't make any sense so there's no valid solution".

I got that a few times and it's a good sign I have a senior candidate.

The real-world use case is simple when you imagine that I want to get a JSON payload describing different car configurations, possibly for a "car configurator" on a sales website, or perhaps for a videogame where there are different cars with different attributes at random. Once I go from "make a car" to "give me some json" everyone started to see it's as a less fictitious problem.