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?
Right? Magic is real in Dune, we don’t don’t need a hard sci fi reason for every missing technology frank Herbert didn’t think of in 1965.
Nukes play a rather pivotal role in Herbert’s book though. He definitely thought of them.