Fun fact:
The solid rocket boosters on the Space Launch System are the size they are because they are old Space Shuttle Boosters. The engineers would have preferred larger, more powerful ones, but that's the size available.
Engineers at the time also would have preferred larger ones, but the boosters needed to be shipped by rail and thus were limited to the standard sizes of rail lines in the US, including tunnels and overhead obstacles.
Those are the size they are (4 ft 8.5 inches apart) because the US inherited standard gauge rail from the British, who built the first ones in North America.
And those are the size THEY are because the people who built the first rails in Britain had the same tools and parts used to make wagons. Other sizes were risky because if you ran a non-standard spacing and one wheel fell into a rut, you risked breaking a wheel.
And THOSE were the size they were because they were built to accommodate the existing ruts on European roads, which themselves were first built by the ancient Romans to accommodate their war chariots. The standard gauge we have in the US and most of the world today is the same as the wheel spacing on Roman war chariots, also standardized for the same reasons of avoiding broken wheels.
And THOSE were built to accommodate two standard sized horses side by side, hip to hip.
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So basically, the most powerful rocket boosters in the world today are the size they are - and no bigger - because of limitations introduced by the size of a Roman horse's ass more than 2,000 years ago.