>>64497620
Aragorn only starts wearing armor (mail) at Helm's Deep, and yes it was done to keep his overall design in line with the ranger visual. PJ actually wanted Aragorn to be in Gondorian armor at the Battle of the Black Gate (since he is now directly leading Gondor) but Viggo thought it would make sense for Aragorn's fighting style, and they compromised (he has bits of plate but is still mostly wearing mail, and the outfit is inspired by Elendil's get up in the FotR). However PJ put Viggo in the armored outfit for the coronoation, pic related.

Honestly though, the mail is far far closer to what Tolkien envisioned though. Tolkien makes almost no reference to plate throughout the books (there's Imrahil's vambraces, and some mentions of iron collars and that's about it) and the vast majority of warriors from the West are wearing mail, while the East and South get some mentions of scales and lamellar like armor/