Not in the days when these BIOSes were written, but in the early eighties, yes; the original IBM MDA card had only 4kB memory (enough for just one screen of tex

Not in the days when these BIOSes were written, but in the early eighties, yes; the original IBM MDA card had only 4kB memory (enough for just one screen of text) because memory was expensive. So sticking to 80x25 was kind of important back then.