As the title says.
In truth, I know the reason: SE wanted Ramuh to be another EX primal grindfest that players didn't actually bite on, preferring mostly to work on their (superior ILvl) Relic Nexus weapons. But, now that Shiva is dropping weapons at the exact same item level as Ramuh, and that her weapons are dropping every time with every victory, is there really any need to keep Ramuh weapons so rare?
Just like SE upped the drop rate on Mirrors of the Whorl, they should up the drop rate on Ramuh weapons.