I'd like to be completely on board with
@TheFatBlueCat and come to terms with respectfully consuming and honouring home hatched cockerels, but the lessons we learn as children are the deepest and I spent a LONG time arguing for a pet when I was a kid, which was disallowed until I was a young adult earning my own money. That experience led me to place a very high value on the pets I keep - they're not taken for granted.
It took me quite a while to build a commitment to hatching eggs under a hen because of the cockerel question. Your argument that it's good for a hen is clear and IMO doesn't even need evidence. It was the vet who finally won me over when we discussed it and he said the cockerel would've had an amazing life and then a humane death, he won't have lived as though his life was short, he'd have lived joyfully, then he'll simply go to sleep and not wake up.
The other factor in South Australia (probably all of Australia) is that we don't really have the kind of hatcheries the Americans have. We're more like NZ in that hatcheries serve the food industry, with a mere few 100 birds sent to small retail outlets (often family-owned fodder and grain stores) to eventually find homes in people's backyards among the millions of birds hatched to feed humans one way or another.
Many backyard chickens are not from hatcheries at all, but from breeders who focus on breed standards and showing, and who sell the pullets who are not up to standard into backyard flocks. Other breeders focus on the backyard market, producing pretty crosses like Ivy and Peggy at my house. Sometimes buyers go direct to breeders, Ribh does this; sometimes breeders place their pullets in small retail outlets, perhaps even alongside the ones from the industrial hatcheries.
So it's possible for us to source pullets that were more ethically bred, raised, and converted to commodity with greater humility than the Americans can.
These features of the Australian pullet market are a minor disincentive to hatching your own. An incentive to hatching your own is that you're not introducing viruses or bacteria that you're not already coping with. For me, that holds some appeal.