FathimaH, for me i think, its because the conflict between muslims and jews, as you know that birth of Muhammad S.A.W.W took place on Arab land and in arab tribe, and Jews wanted the last prophet on their land and in there tribe. now Jews are not doing any thing muslims are doing or following.. and Prophet Ibrahim was muslim, and the religion of Ibrahim A.S was same as our Last Prophet Muhammad S.A.W.W, and we are practicing almost many things what Prophet Ibrahim A.S did, like this Qurbani, Hajj,
though these all should be the part of there religion also, but they diverted from the right path. and were counted in non believers..