Have you ever thought about this question—if a flight insurance product promises automatic claims but can't even tell if the flight is really delayed, what’s its value? Similarly, if a decentralized lending platform cannot obtain real-time ETH prices promptly, how can it safely execute liquidations?

This reveals a fundamental dilemma in the blockchain world: on-chain data is highly certain, while off-chain data is a tangled mess.

Imagine blockchain as a sophisticated large clockwork system. Thousands of computers, following perfectly consistent rules (i.e., code), verify and synchronize each transaction one by one, ensuring all pointers point to the same state. This certainty is the source of trust—if the input is the same, the output must be the same, leaving no room for ambiguity.

But here’s the problem. This perfect system is essentially an "island." It cannot proactively look outside the window to check the weather, access real-time stock prices, or verify who won a football match. Blockchain cannot see or touch the real world.

If each node tries to look up information online independently, it will inevitably receive a variety of answers—different delays, data source discrepancies—causing the consensus mechanism to collapse on the spot. So, blockchain simply makes a choice: to isolate itself from the outside world actively, maintaining internal purity and consistency.

However, this approach pushes smart contracts into a dead end. They possess incredibly powerful automatic execution capabilities but are hamstrung by being "cut off from the world," rendering them unable to handle most real-world business scenarios. It’s like having a top-of-the-line computer that has never connected to the internet—full of potential but stuck right there.