In the Dune universe, when a laser weapons hits a shield, both are destroyed in a nuclear explosion reaction.
So instead of building nuclear weapons, wouldn’t it be easier to tie a timer and a “parachute” to a laser gun and drop it from orbit onto your enemy’s city?
Shields and lasguns were available to a significant number of fighters. If you were able to accurately hit a shield with a lasgun, you were probably within the blast radius too.