Why didn’t Ravana take the help of the Nivatakavachas during the Ramayana War?

Why didn’t Ravana take the help of the Nivatakavachas during the Ramayana War? Ravana had the army strength of Shath kodi sahasram. That is One trillion demons..and even the weakest foot soldier of Ravana were more powerful than Nivatakavachas.. 'The number of demons in Lanka is reported to be a hundred thousand crore, three lakh, ninetynine thousand and six hundred. ~Kishkindha Kanda Section 35 In addition to this Ravana single handedly demolished Nivatakavachas in Treta yuga. Thou didst, by thy prowess, use to give vent to haughty words before the enemies; thou wert the maintainer of thy kinsmen and servants and the slayer of many perpetrating dreadful deeds; thou wert the destroyer of thousands of celestials, Dānavas and Yakshas; thou wert the subduer of Nivata Kavachas in the encounter; thou didst hinder the performance of many sacrifices and wert the protector of thy relatives; thou wert the obstructer of pious observances. ~Yudha kanda Section 112 So their army might would bring near to zero value to Ravana's army. Adding 3 crore demons to 1 lakh crore would practically be USELESS. Hence Ravana didn't bothered to call for aid.