Because that is the meaning of the word. It has no other meaning. Why would you condone error. I have already demonstrated this in a multitude of different English translations, as well as some translations in other languages. Do you think that they are all wrong. Everyone but the KJV translators are wrong. Surely you have more sense than that. I have demonstrated to you that the meaning of the word is passover. A Greek lexicon gives that definition. There is no other definition. How can you possibly think that out of 29 times when the word is used the KJV translators translated it wrong 28 times?
It is not the duty of the translator to interpret a passage, but rather to translate the passage. We don't need their Anglican interpretation. We need the interpretation of the word from the Greek. If the translators simply give their interpretation they are no better than those that paraphrase. We have enough paraphrases on the market, and they all stink. I'll give you an example:
Ecclesiastes 6:9 Better is the sight of the eyes than the wandering of the desire: this is also vanity and vexation of spirit.
In the Living Bible, Kenneth Taylor paraphrases this verse instead of translates it. Here is his paraphrase:
"A bird in the hand is worth two in the bush."
--He gave his thought on the verse, what he thought it should mean, not what it meant.
The same is true in Acts 12:4 with the KJV translators with the word "pascha." They gave an interpretation--what they thought the word should mean, not what the word meant. It was an interpretation, not a translation.