It was popular in England when he was a lad, that's why. In 1878, when the song was first a 'hit' here, he was 13, and at school in Devon; Stalkey and Co, as you know, was based on his own schooldays. He was always keen on such aspects of popular culture, and much influenced by them. As to why that particular song, I suppose that it must have been a special favourite at the United Services College.