Why don't Western Roman infantry have pila?

[Oedipus's Stepdad]

They have that weird dart that does less damage than the pilum. Eastern legions have them, I don't understand why their western counterpart do not? Also should I replace my tier 2 legio comitatensis with the tier 3 elite infantry that lacks ranged weapons against the huns?

[tribunodelaplebe]

By this time period the roman army had largely abandoned the pilum and started utilizing the plumbata, wich is the dart most roman infantry in the game uses. The only units that use the pila if i recall correctly are the Eastern Armoured Legio (ERE) and the Cornuti Seniores (WRE).
https://youtu.be/bau0madVNc4