The vertical height of characters was dictated by the number of scan lines in the display. It was impractical to use displays that weren't compatible with TV st

The vertical height of characters was dictated by the number of scan lines in the display. It was impractical to use displays that weren't compatible with TV standards, so that meant 240 non-interlaced scan lines. 10 pixels is about the smallest height you can make a font including line spacing, so that's how you get 24 rows. Once you have the number of rows, you want the number of columns to have a good balance. 80 columns gives you well proportioned characters, where other alternatives e.g. 132 do not. Add that to the historic precedence and you have the makings of a standard. Teletypes were in common use on the first time-sharing systems, and those were only 72 columns wide. Consider yourself lucky to have those extra 8 characters.