In ancient societies such as the Egyptians or Viking-age Norse grave goods were meant to be of use to the dead in the afterlife.

What use would a bow be to an Elvish soul in the Halls of Mandos?

Also, as the barrows on the Barrow Downs were originally the graves of the Dunedain nobility of Cardolan (who would have believed in Eru), would they have thought that armour, weapons and jewels might follow a human soul beyond Arda?

Perhaps this shows a little inconsistency in Tolkien's "Sub-creation"? Lavish burials smack of the heroic, as in Beowulf, but seem odd in a monotheist setting. Can you have Christ and Odin at the same time?

: : The reference to Beleg Cuthalion reminded me of Thorin's burial and the Barrow where the hobbits were imprisoned.

: : Apparently funerary customs were similar among Middle-earth's peoples (although that's drawing a LARGE inference from three burials spaced out over a great arc of time).

: : I mean, warriors were buried with their weapons and women were buried with jewelry.

: : Boromir's funeral comes to mind too.

: : It's small touches like these which always increase my appreciation for Middle-earth. There are so many things Tolkien put into the stories which other authors might not have considered.

: : Michael

: I didn´t knew about wemen, but as for warriors, especially died in battle, (my opinion) they were buried with their wapons and the ones of the beaten as a ceremony and a reminder of the honor and power of this brave fighter.
: Something like a warning for enemies and a sacred place for allies.

: Beren Meldon Nárondorello