Comment by T-A

The first working transistors and engines were of the size which happened to be most convenient to work with. They could then be shrunk because fundamental physical limits to their size were far below human scale. Their inventors were neither constrained by nor interested in those fundamental physical limits. They were inventors, not scientists.

In contrast, a particle accelerator like the LHC is designed from the outset to explore physics at a given energy scale at the lowest possible cost. Shrink it any further and it will no longer work. Despite decades of attempts to come up with alternative designs, when time comes to draw up plans for a successor capable of pushing to even higher energy, it's just more of the same:

https://home.cern/science/accelerators/future-circular-colli...