Imagine you're given a problem that is completely novel in its description yet is actually reducible in some non-trivial way to a well-known NP-complete problem that has great probabilistic algorithms available for it.

Googling the original problem description will (for a novel formulation of the problem) not result in any advantage and implementing a standard algorithm will not work if you need n to be large for your application.

I will admit that it's a slightly contrived example ;)