Think of the people Banjo was writing for, and the time. It was just after Federation and he was helping to build an Australian identity, one rich with heroes and larrikins that the common man could relate to, now that we'd given Britain the arse (well, half-arse anyway) and had a relatively class-free society, which at the time was reasonably close to a meritocracy. No romances about lords and ladies mooning about in fancy clothes were going to cut it in Australia -- and as the population was sparse, so education was a difficult prospect, they needed ballads with rich meter and rhyme as mnemonics to create a new "tradition". It is the simplicity that is their greatest virtue. No, the form is not difficult to write -- but then, I don't consider any form particularly difficult. It's the yarn, the mood and the characters that are important.
I'll do a copy paste and shift this to the Poetry Discussion forum though.
It could be worse