Tradition

YHWH has told us to remember and observe His Set Apart times for us: 

Passover/Unleavened Bread, Feast of the Harvest/Weeks (Shavuot/Pentecost), Day of Trumpets, Day of Atonement, and Tabernacles (Leviticus 23). 

These are not 'Jewish Holidays' as there were no such people back in that day -- His People were Hebrews and the mixed multitude that came with them out of Egypt. Jewish Holidays are the man made traditions of celebrating Hanukkah and Purim for example. 

Quoted from Judaism 101: 

Chanukkah is probably one of the best known Jewish holidays, not because of any great religious significance, but because of its proximity to Christmas. Many non-Jews (and even many assimilated Jews!) think of this holiday as the Jewish Christmas, adopting many of the Christmas customs, such as elaborate gift-giving and decoration. It is bitterly ironic that this holiday, which has its roots in a revolution against assimilation and the suppression of Jewish religion, has become the most assimilated, secular holiday on our calendar. (end quote). 

The Chanukkah tradition, as recorded in the Talmud: at the time of the rededication, there was very little oil left that had not been defiled by the Greeks. Oil was needed for the menorah in the Temple, which was supposed to burn throughout the night every night. There was only enough oil to burn for one day, yet miraculously, it burned for eight days, the time needed to prepare a fresh supply of oil for the menorah. An eight day festival was declared to commemorate this miracle of the oil.

(note: the Talmud is a collection of oral tradition of Torah interpretation according to Rabbinic Judaism.)

Our Creator was never about religions. His perfect governing system was for our health and well being, fair and just. Remembering important events is not the issue - it's the celebrations of them year after year as holidays that goes against what God said especially when His appointments for us are ignored by most.