The word(s) "why" appears 48 time(s) in 45 verse(s) in Quran in Muhammad Pickthal translation.

(1) And when it is said unto them: Believe in that which Allah hath revealed, they say: We believe in that which was revealed unto us. And they disbelieve in that which cometh after it, though it is the truth confirming that which they possess. Say (unto them, O Muhammad): why then slew ye the prophets of Allah aforetime, if ye are (indeed) believers?

(2) And those who have no knowledge say: why doth not Allah speak unto us, or some sign come unto us? Even thus, as they now speak, spake those (who were) before them. Their hearts are all alike. We have made clear the revelations for people who are sure.

(3) Bethink thee of the leaders of the Children of Israel after Moses, how they said unto a prophet whom they had: Set up for us a king and we will fight in Allah's way. He said: Would ye then refrain from fighting if fighting were prescribed for you? They said: why should we not fight in Allah's way when we have been driven from our dwellings with our children? Yet, when fighting was prescribed for them, they turned away, all save a few of them. Allah is aware of evil-doers.

(4) O People of the Scripture! why will ye argue about Abraham, when the Torah and the Gospel were not revealed till after him? Have ye then no sense?

(5) Lo! ye are those who argue about that whereof ye have some knowledge: why then argue ye concerning that whereof ye have no knowledge? Allah knoweth. Ye know not.

(6) O People of the Scripture! why disbelieve ye in the revelations of Allah, when ye (yourselves) bear witness (to their truth)?

(7) O People of the Scripture! why confound ye truth with falsehood and knowingly conceal the truth?

(8) Say: O People of the Scripture! why disbelieve ye in the revelations of Allah, when Allah (Himself) is Witness of what ye do?

(9) Say: O People of the Scripture! why drive ye back believers from the way of Allah, seeking to make it crooked, when ye are witnesses (to Allah's guidance)? Allah is not unaware of what ye do.

(10) (The same are) those who say: Lo! Allah hath charged us that we believe not in any messenger until he bring us an offering which fire (from heaven) shall devour. Say (unto them, O Muhammad): Messengers came unto you before me with miracles, and with that (very miracle) which ye describe. why then did ye slay them? (Answer that) if ye are truthful!