I think this is because how it's implemented. In the USA I've mostly seen it implemented as a grid of bubbles because it's better for machines to process, and I

I think this is because how it's implemented. In the USA I've mostly seen it implemented as a grid of bubbles because it's better for machines to process, and I found it pretty confusing at first (see https://www.fairvote.org/rcv_ballot_design https://www.fairvote.org/rcv_ballot_design), imagine this for 20+ candidates like Queensland often has. I think the Australian system of writing the numbers in boxes is way easier to follow, though I don't know what happens if you fill them in wrong. The ideal solution IMO is a touch screen machine with a list of candidates, you drag and drop your order of preference, then when you're done it prints out a paper ballot which you can double check is correct then drop in the ballot box.