Believe it or not, engineers were heavy users of BASIC in the first few years. And FORTRAN was created with the notion of matrix multiplication, so it was just natural that BASIC implementations supported matrix multiplication.
My grandfather was a construction engineer. I remember visiting his office around 1990 just before he retired.
His only computer was a Commodore 64 and he had written all the software himself in BASIC over the years, just translating a lifetime of professional experience into these little interactive programs on floppies.
Maybe the modern equivalent would be to use Excel.
