No idea if this was a factor, but 80x25 on the IBM PC allows for showing 80x24 plus that extra line of function key labels:
https://en.wikipedia.org/wiki/IBM_BASIC#/media/File%3AIBM_Ca... (IBM BASIC screenshot)
Imagine when edit.com came out and QBASIC used it for the editor. You lost two more lines of valuable code space!
https://en.wikipedia.org/wiki/MS-DOS_Editor#/media/File%3AMS...
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