It makes sense for the publisher to do so, but I think eBook makers (Kobo, iBooks, Kindle) might have more to lose if books aren’t DRM protected
this points to a good critique of the work, but it doesn't come out and say it explicitly. It seems to me that you are suggesting that the essay overlooks device maker's interest in DRMs. If so, this is a large oversight, and one that could have again become the focus of the essay.