I don’t understand how it evolved to be made in that form factor, and why it is still being done that way.

I have semi good news for you. There are several sizes of newspaper, however, some newspapers are only available in certain sizes.

https://en.wikipedia.org/wiki/Newspaper_format#Sizes_and_aspect_ratios

• Broadsheet 749 mm × 597 mm (29.5 in × 23.5 in) (1.255 aspect ratio)
• Nordisch 570 mm × 400 mm (22 in × 16 in) (1.425 aspect ratio)
• Rhenish around 520 mm × 350 mm (20 in × 14 in) (1.486 aspect ratio)
• Swiss (Neue Zürcher Zeitung) 475 mm × 320 mm (18.7 in × 12.6 in) (1.484 aspect ratio)
• Berliner 470 mm × 315 mm (18.5 in × 12.4 in) (1.492 aspect ratio)
• Tabloid 430 mm × 280 mm (17 in × 11 in) (1.536 aspect ratio)
• Demitab (half tabloid) 200 mm × 270 mm (8 in × 10.5 in) 1.3125 aspect ratio. “Magazine format”, though many magazines are larger. Used by The Economist.

perhaps your physical newspaper is available in an alternate size?