Why does Willa Cather compose My Antonia from a male point of view?

Have read only a little way into Willa Cather's 1918 novel "My Antonia," so don't have a whole lot to say at this point, but noted a few things: First, was surprised that that narrator is a male. I'd read the novel many years ago and had completely forgotten that. Why is that important for Cather to do? Why does she need to structure this novel from a man's point of view, first-person no less? Must have something to do with the dynamic between the narrator - Jim? - and the Czech immigrant neighbor, the eponymous Antonia. But there's another element as well: The opening chapters, which pretty much just set up the conditions for the novel - as noted, we barely even glimpse Antonia - are imbued with loneliness and with a sense of the American West and the frontier ethos that is, today, completely consigned to the world of myth. The narrator very matter-of-fact tells us that he's been orphaned (he seems to be about 10 to 12?) and sent from his East Cost home to live with his grandparents in Nebraska. Obviously he hardly knows them, and vice versa. He rides a train out West, pretty much unsupervised, and gets picked up at the station and driven (by cariage of course - setting seems to be late 19th century) to a fairly remote farm in a small town. By today's standards of child-rearing and responsibility, this would be a terrifying journey - material for a whole novel right there - but in the time in seemed to have been a much more acceptable or conventional social arrangement - Jim just adjusts right away to his completely new and alien life. In this sense, I think Cather chose to have a male protagonist because she didn't want to delve into issues of feminism and the expectations of women and women's independence - at least not through her protagonist - and a male protagonist was much more "acceptable" as an independent agent to readers of her time, and maybe later. It would have been a very different topical ground if she had simply written the novel in first person, seemingly like memoir, without the frame story in which an old friend whom she encounters on a train ride leaves her a manuscript he's composed. And that's my 2nd point: frame stories were very vougueish in 19th century and early Modern fiction (e.g., Conrad), and I'm not sure why but they seem to be a bridge between the omniscient 19th-century narrator and the familiar first-person confessional of most 20th-century fiction. Finally, the novel has a documentary feeling to it: Cather is expert at capturing all of the physical nuances of a time and place, and My Antonia is almost a time-capsule record of prairie life long gone.