Good point! Minicomputers were around before micros. So BASIC wasn't born in a vacuum. Lots of precedent.

What's relevant is, modern ideas of encapsulation, object-oriented design or even structured design were not available to the inventors of early language ROMs. Nor did they have the room for such luxuries. They wrote one blob of code, probably in one large .asm file, that got the job done.

They were available as Fortran, LISP, C and Pascal were all around back then. But you're right about the necessity code the ROMs in Assembly .