Cause we all follow the laws in Leviticus? You don't do anything from friday night till sunday morning and sacrifice your livestock on a pillar of flames in Jerusalem?
Old Testament is consider a sort of religious story book with lessons and record of thing that were and God's love and such, not verbatim truth and law. The New Testament is a bit more true and accurate in the eyes of most church but still not an exact account.
Matthew 5:17. Jesus says:
Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.
Meaning true Christians can't ignore the laws of the old testament.