Why does IR propaganda never use Sassanid Iran?

From what I can tell, the focus purely on history of Iran after conquest by Caliphate. Just practically speaking, wouldn' it serve their propaganda well to glorify Sassanid Era also? IR regime heavily leans on propaganda of themselves being bastion of resistance against "the West", so it seems stupid for them not to tap into Sassanid history given how they resist and score many victories against the Roman Empire, which is literally the father of "the West". Why do they neglect Sassanids in this capacity?