Here's why:
* Pinocchio's nose grew whenever he told a lie. This makes the act of "poking his nose" a metaphor for something that's impossible or highly improbable.
* Waiting for Pinocchio to poke his nose implies waiting for an event that is so unlikely, it's practically a joke. It's a way of expressing frustration or disbelief about something that seems unlikely to happen.
Example:
* "Don't hold your breath waiting for them to apologize. You're basically waiting for Pinocchio to poke his nose."
In essence, the phrase emphasizes the futility of waiting for something that is highly improbable or impossible.