If Passover is a Jewish holiday, one might ask, why do some Christian churches celebrate the holiday? One reason is that Jesus was a Jew. Jesus celebrated Jewish holidays, including Passover. Some experts even think that the Last Supper was actually a Passover Seder.
Some Churches may host a Seder in order to let worshippers experience an authentic Last Supper. They may want to eat a meal as Jesus did. However, the Seder has probably evolved significantly since the time of Jesus and this may not be practical.
Another reason to celebrate Passover is that Christians have an English version of the Torah in their bible. They call it the Old Testament. Passover is a retelling of the bible story in the Book of Exodus of the Jews being slaves in Egypt, and how they escaped. In Exodus, it says that Moses went to Pharaoh, the King of Egypt, and told him “Let my people go.” But he refused. Then the Lord inflicted ten plagues on the Egyptians. The ten plagues were water that turned into blood, an overwhelming infestation of frogs, an inundation of lice, swarms of flies, cattle disease that only affected the Egyptian cattle, boils that were only on the Egyptian’s skin, hail that only destroyed the Egyptian’s crops, locusts that ate only the Egyptian crops, three days of darkness for the Egyptians while the Jews had light, and the death of the Egyptian firstborn children and livestock. Then Pharaoh let the Jews go. However, he changed his mind and chased them. But Moses parted the Red Sea and they escaped into the desert.
Another reason is to develop a deeper understanding of a related faith from which Christianity had its roots. Finally, to some extent, everyone is enslaved by something. Celebrating Passover provides an opportunity to recognize how we are enslaved. For example, someone might be enslaved by an addiction to video games, drugs, or work.