This is great! Thanks for summing up what I meant by always has been horizontal!
Though I wrote about the pen paper analogy, I completely forgot to talk about the command lines. Great that you brought it up. Though I think there is a minuscule percentage of people who have inherently imbibed directions from CLI when compared to writing and then mobile phones, hence would be okay to be disregarded.
The Arabic and the oriental systems both enforce horizontal nature, which I is what am writing about. The difference being the direction. Will have to see some Arabic origin timelines from right to left.
Papyrus Scrolls are in never ending portraits since we cannot read much horizontally longer sentences. This would also be where the news feed takes it from. However the point here of timelines, I feel that one would request to use a landscape to depict it and not be comfortable with a portrait timeline when asked to draw.
Technology too developed in such a way that rasterisation of pixels take place from top left to bottom right in a vertical format, this too may be because of the papyrus scrolls.