I'm not an expert but, certainly, (1) limited memory on historical machines necessitated a small-width representation of a real number; (2) limited cpus meant s

I'm not an expert but, certainly, (1) limited memory on historical machines necessitated a small-width representation of a real number; (2) limited cpus meant simple operations needed to be applied to this small-width representation in one go. Ie., your CPU is just a system for taking bit patterns and producing new bit patterns: (0000 0000) -> (1010 0101). So you want each individual number to be of a size the processor can operate on in one pass. By using two integers you gain some capacity (ie., you can still overflow), but lose memory and compute performance.