Our chippie member asked the question’why is the hole the size it is’.
Answer from a wacky wiki —
The size they decided on was 4.25 inches in diameter. The reason is that the folks at Musselburgh (now a 9-hole municipal course and called Royal Musselburgh Golf Club) had invented, in 1829, the first known hole-cutter. That ancient hole-cutter is still in existence and is on display at Royal Musselburgh.
That first hole-cutter utilized a cutting tool that was, you guessed it, 4.25 inches in diameter. The folks running the R&A apparently liked that size and so adopted it in their rules for 1891. And as was usually the case, the rest of the golf world followed in the footsteps of the R&A.
The exact reasons for why that first tool cut holes at the now-standard diameter are lost to history. But it was almost certainly a completely arbitrary thing, a notion supported by the story that the tool was built from some excess pipe that was laying about the Musselburgh links.