Yes, I agree somewhat that part of it is comertialization. But can we agree that there are many different kinds of troops in real life? And different ranks too.
Besides, didn't the Empire have different divisions, too? There were stormies, sandtroopers, shadow troopers, TIE pilots, snowtroopers, scout troopers, imperial troopers, ect.
But I know where you're coming from, we like our BPs for army builders, not with random figs. Your argument is just flawed.