There was actually no "thought" being put into the IEEE spec as such. It was merely a codification of the design of the Intel FPU (only one of many, very different implementations of FP units pre-standardisation). There was thought put into that implementation, but the "standard" is merely a codification of that design.

It has many many warts, and many design choices were made given the constraints of hardware of that time, not by considerations in terms of a standard.