Because the shadow of Christ is on every page of the Old Testament and is explicit on every page of the New Testament.
All believing Jews and Gentiles will be saved by the blood of Christ.
To miss this, IMO, is to miss the entire point of creation. God planned from all eternity who and why He would save. He's not just winging this. He knows what He's doing and He does what He has decreed.
Saved by grace through faith in Jesus Christ.
What better way to muzzle Christians than to say the word does not have to be proclaimed to everyone? God does not see us as races. The only blood that saves is the shed blood of Jesus Christ, available to all the world if they would but see and hear and be saved.
OF COURSE
ALL SAVED will be SAVED BY THE BLOOD OF JESUS AND FAITH IN HIM.
The route there is different for individuals. Certainly it can be different for people groups.