Curtain Jerker
Donor
'Development' isn't a straight line. Even the idea of 'progress' being this automatic always-forward-moving thing is problematic. Historiographically, it's fallacious and somewhat backwards-projecting.
You might as well ask why it took us so long to develop nuclear weapons, when we have been committing warfare for so long.
This. Real life isn't Civilization 2 where you have tech trees and each technology unlocks the one a level above it til you get to build a spaceship. It just doesn't work that way.