Just curious: why do so many of us use 4:3 story size?

I'm curious about a maybe naïve question.  All the demos I've seen in this community and beyond are formatted in the standard 4:3 story size.  But if you are playing your storyline course in full screen mode of either a laptop or smart phone, that always leaves a large gap on the left and right of the screen.  That's lost space that could be incorporated into the course if only to give in a more roomy feel.  (This is assuming you're not using the menu or other player functions that would make the course wider on the screen.)  So why don't even just a few folks demo a shorter-wider size that would better fit a laptop or smart phone?

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