Base prime weapon reacquisition

Is there a reason why we can't get the base prime weapon again after upgrading a prime to stage 3? Base prime weapons have a different name than the upgraded versions, yet when I tried to reacquire the base prime weapon after upgrading to stage 3, in my case prime horn, the npc offers the base weapon but after hitting buy, there is a message "prime horn cannot be obtained"

Stage 3 removes the dot effect from the weapon and it would be a great help to be able to get the base prime weapon as these allow any job to self wake themselves when slept.

I would like to see this change as well. We're allowed to re-acquire every other possible weapon from their sources: Relic weapons as drops from monsters, Empyrean from splintered chest in Rulude Gardens, Mythic by re-farming in Nyzule Isle).

I want to be able to re-acquired the weapon and use it is a preventive measure for Damage-Over-Time (DOT) which will wake us from Sleep effects, as VoiceMemo has already stated.