Dispensationalism, that's why. Dispensationalism is a way of interpreting the Bible that sees (among other things) the promises God made to Abraham in Genesis 12, 15, and 17 as properly belonging only to the Jews as an ethnic people, and therefore they are seen as God's true covenant people, while the New Testament Church is seen as an historical parenthesis. God will therefore eventually take up fulfilling his promises to his true covenant people, the Jews, once he is finished with his plan for the Church. This teaching is directly contradictory to the teaching of the Apostles, who expressly applied the promises made to Abraham to the New Testament Church. See Acts 2:39 as a repetition of God's promise in Genesis 17:7-8, but expanded to include "all who are far off," that is Gentiles who would come to faith in the Messiah. Likewise, Paul tells the church in Rome that they are children of Abraham by sharing in the same faith that Abraham had in Romans 4, especially verses 9-17. Paul repeats this teaching even more explicitly in Galatians 3:5-9, where he says: > "Does he who supplies the Spirit to you and works miracles among you do so by works of the law, or by hearing with faith--just as Abraham "believed God, and it was counted to him as righteousness"? Know then that it is those of faith who are the sons of Abraham. And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, "In you shall all the nations be blessed." So then, those who are of faith are blessed along with Abraham, the man of faith." The final nail in the coffin of the Dispensationalist's improper hermeneutic, in my opinion, is found in Romans 9, though. There Paul describes the nature of the relation of the Gentiles who are coming to faith in Jesus to those Jews who apostatize by rejecting him. The description is that of an olive tree, where the natural branches that reject Christ are cut off, while the wild branches (Gentiles) are grafted in. Into what? Into "Israel," as he calls it in verse 26. Gentiles who come to faith are grafted into Israel, God's covenant people, and Jews who reject Jesus are cut off. They no longer have any claim on the promises made to Abraham and no right to call themselves God's people whatsoever. In order to regain that claim, they must come to faith in the promised messiah, Jesus Christ.