and Christians and Jews are not on the religion of Prophet Abraham A.S, they are followers of Prophet Easa and Mosa A.S,
so they had then different festivals and celebration occasions.. we Muslims are on religion of Prophet Muhammad and Prophet Abraham, as you know already, and said in your comment also.. while they just followed the Prophet Musa and Prophet Eesa A.S, they were not the followers of Prophet Abraham A.S,

lemme try to explain little more, see first Prophet Musa came, when the people diverted from the correct path, and were going on wrong side, those one are called Jewish, then after some time can a century of more Prophet Eesa A.S came, and he tried to keep them on the right path. some how he succeeded, but still many of them were on wrong paths.
and the problem was the people were not following the religion of the last prophet 100%, they made many changes in the holy book,

pardon if any mistake, or poor English, since am not that good in it, and its not my first language also.