Has a "reasonable" positive identification ever been made on any of the grave sites of any of the Apostles? (I don't know.) I'm sure there are plenty who "believe" that so-and-so is buried "here", and churches have probably been built on such beliefs. I'm just wondering if there is a widely accepted consensus in any particular case. To my knowledge, even the tomb of Christ has not been positively identified.
God left pretty much nothing material to become the site of false worship or war. The ark of the covenant was lost along with the tablets. The relics of the cross and the icon that wasn't painted are legends or legendary as is the famous shroud of Turin.
The lack of any material evidence of God, even much historical evidence of Christ Himself, is an interesting and provoking thread that has not changed much in time. The holiest of things God gave us have been lost or are hidden. God is immaterial and faith is as well. We must not put our faith into material things even if they represnet true relics. The recent return of the relics of two saints to Constantinople was a reminder that such relics often involved men killing each other over them. Mary's tomb would have easily become an object of worship. The Apostles cleverly do not mention her much precisely in order not to distract from the message of the Gospels and in order not to make her an object of worship, or something people would fight over. Reverence yes, worship no.