Helps to ensure you’re only talking to people well-equipped to solve the problem you have
Helps to avoid dodgy people / service providers who will promise the world, send invoices, and deliver mediocrity six months late
What does the test entail?
The Orange Juice Test has nothing really to do with orange juice. It’s just named after one particular application of the test in which it’s used to select a conference hotel based on whether than can meet an extremely challenging banquet request. But you can use the test for selecting any service.
The idea is to propose a task that's extremely difficult but possible then measure the candidate’s reaction. If they are defeatist (“That can’t be done!“) or deluded (“I’d code that in a weekend“) they fail. If they say "That’s a real problem. I can help you with it, … and this is how much it will cost," they pass.