Quote: "neilithicman"
The half crown wasn't the largest UK coin, the UK had a full crown that circulated up until Edward VII and then they were only commemorative from George V on.
Perhaps they didn't like them because there wasn't much difference in size an value between the florin and half crown so it was a bit pointless to have both?
Uh....
I don't think so.
"By 1751 the popularity of the silver crown had declined and it evidently played a limited role in circulation. An attempt at revival was made in 1818 when Pistrucci’s head of George III was combined with his classic St George and the dragon to produce what was said to be one of the handsomest coins in Europe. But the crown failed to re-establish itself as a circulating coin, and was to do so again at the end of the century despite active efforts to promote its use."
I'll give you the fact of whether they circulated
at all, but were they really a "circulating denomination commonly seen by most people in daily life"? They were certainly nowhere nearly as commonly used in the UK as the half crown, since decades before James Cook ever even set foot on Australia and certainly not by the turn of the 20th century.
But back to Australia; I think I solved my own enquiry:
https://www.cointalk.com/threads/australia-half-crown-coins.140517/
It mentions there that Australia wanted to decimalise their coinage as early as 1902 and issue coins at par with a decimalised British pound sterling, with 10 florins in a pound, and a florin being 100 cents, a shilling 50 cents, and a sixpence 25 cents, but the half crown (125 cents) would have been an odd denomination out; so ultimately they left it out.
When the British got back to them pointing out that they weren't planning on doing that decimalising any time soon, the Coinage Act of 1909 was amended to make the coins at par with the pre-decimal British pound sterling, but the omission of mention of the half crown was a vestige of that earlier attempt at decimalising straight away.
No crowns (which would have been 250 cents) were mentioned either; and the Act was amended in 1936 to allow for the commemorative 1937-38 Australian coronation crown. Apparently British home coinage, including the 2'6 coins circulated freely in Australia until around 1920 as well, being gradually withdrawn from circulation.