Function approximation was always useful (e.g. autopilots, speech recognition, compression, etc.), the question was what one could do with such a trick when it

Function approximation was always useful (e.g. autopilots, speech recognition, compression, etc.), the question was what one could do with such a trick when it was scaled up. What is the analog for cryptocurrencies? What is the underlying technology in cryptocurrencies that can be scaled up to make them useful like with function approximation?