Why can't you castle when in check?

I personally believe that this rule is meant to "balance" the castling move.

Think about it - castling is already a very powerful move that allows a player to move two pieces at once. Not only that, the two pieces move in a way that is normally prohibited (the King moves two squares, and the Rook jumps over the King).

If a player could simply castle out of check, you could, in theory, leave your King in the centre for as long as you wanted until it is in danger. There would be no point in castling your King into safety at the start of the game. As soon as your King gets attacked, you would be immediately be able to castle out of it.

Just my two cents.

Because castling is a defensive move, you shouldn't be able to avoid a threat with it.

the king is pretty slow, so if he ever moves into check he will be shot down, so he needs to be careful how he hides in his castle. when in check, he kinda gets scared and forgets about castling.

We must never question authority.

ILLEGAL!
https://www.youtube.com/watch?v=lwXJWXgdb4I

Frankly, to enable preventing castling with checks, me thinks.

Havent a clue.

Why does White move first.

Why don't the game end when  you mistakenly move and put your king in check.You touched and moved a piece I think the game should be over,but it is not,same thing.

I dont understand that. Castling is a defensive move (of course there is always the crazy oddball tactics problem where castling is an offensive move), but isn't the whole point of defense to avoid a threat?

I dont see the harm in castling out of check. All it would do is change some strategy in the game. It would be the same rule for everyone.

The same as the en passant rule where you get punished for moving your pawn up two squares in defense. It is to make the game fair. I always hated that you can also not castle through check. Basically, if you are in any kind of "heat", the castle move is not your free ticket out of trouble. This is why they always tell the new player, castle early! 

We should be able to castle while in and through check. Castling is one move, not multiple, so why does the square we pass over count?

Castling requires lots of planning and preparation. The logistics of moving two pieces at once is quite complicated. If the enemy is at your throat, implementing this action is far too difficult to successfully set in motion.

I play on both sites chess.com as well as lichess. Both allow castling even if squares between rook and king are attacked! 

https://www.chess.com/live/game/5292717292 please view this game of mine in which castling is done while I guard the square in between with my queen 

The King cannot cross a square covered by an enemy piece; however, the Rook can. This may be why you've seen this. It is a misconception to think neither the Rook nor King cannot cross an attacked square; it is only the King that cannot. Similarly, all other conditions being met, you can still Castle if the Rook is being attacked. Again, it is only when the King is in check that you cannot castle.

To summarize: The King cannot castle out of, through, or into check. The Rook is fair game . . .

True.  Even some Grandmasters have been flummoxed by the rule, especially with the rook in 0-0-0

The purpose of the rules, as a whole, is to create a game rich in both strategy (long term) and tactics (short term).

Chess is unique in that balance. For example shogi is much more tactical than it is strategic, and go is much more strategic.

Not being able to castle while in check tips the scales towards the tactical. Is it that important? Probably not. Compare it to something like stalemate is a draw (which is a large contributor to the strategic side).