Should you have to swear on the Bible in court?

In a secular society it should not be. A solemn affirmation (or a particular religion's equivalent to an oath on the Bible) should be sufficient. The consequences of perjury are the same whether swearing on the Bible or affirming.

It is not mandatory and never has been. You have a right to simply "affirm" that you will tell the truth, the whole truth, and nothing but the truth. No gods, Bibles, or anything else religious need be involved. Britain has guaranteed a right to affirm rather than swear an oath since 1695. In America, the Constitution specifically recognises the right to affirm as well as to swear. Many Christians do not believe it is right to swear oaths on the Bible and this has been recognised from the beginning of the United States of America (Puritans and Quakers were some of the earliest settlers).

i guess its mandatory as its also swearing to GOD that they will only tell the truth and since bible is the words of GOD aside from Muslim or other religion that doesn't use bible they also have no choice since our government are more into Bible.