Ask the guy who came up with this scenario. But, obviously, we do at some point find it easier to set up side-by-side computers with (relatively) high-latency connections (like, say, ethernet) than to try to put more computing resources together with low-latency connections (like motherboard busses), for physical reasons.

Reminds me of the story about the galaxy spanning AI in the Dune series. With a latency of 10000 light years between it's various instances.

How did they physically get the machines so far apart in the first place? No wormholes??

They had FTL capable ships. The AI used to sync updates using that.

Same reason why culture matters more than individual IQ. Most of human progress is cause because there are many people learn from each other and making millions of tiny improvements over time.