AAVE：COOLDOWN_SECONDS and UNSTAKE_WINDOW

Question

AAVE V1 's redeem() function requires us to wait for COOLDOWN_SECONDS and withdraw money in UNSTAKE_WINDOW.

  /**
   * @dev Redeems staked tokens, and stop earning rewards
   * @param to Address to redeem to
   * @param amount Amount to redeem
   **/
  function redeem(address to, uint256 amount) external override {
    require(amount != 0, 'INVALID_ZERO_AMOUNT');

    uint256 cooldownStartTimestamp = stakersCooldowns[msg.sender];

    require(
      block.timestamp > cooldownStartTimestamp.add(COOLDOWN_SECONDS),
      'INSUFFICIENT_COOLDOWN'
    );
    require(
      block.timestamp.sub(cooldownStartTimestamp.add(COOLDOWN_SECONDS)) <= UNSTAKE_WINDOW,
      'UNSTAKE_WINDOW_FINISHED'
    );
    uint256 balanceOfMessageSender = balanceOf(msg.sender);

    uint256 amountToRedeem = (amount > balanceOfMessageSender) ? balanceOfMessageSender : amount;

    _updateCurrentUnclaimedRewards(msg.sender, balanceOfMessageSender, true);

    _burn(msg.sender, amountToRedeem);

    if (balanceOfMessageSender.sub(amountToRedeem) == 0) {
      stakersCooldowns[msg.sender] = 0;
    }

    IERC20(STAKED_TOKEN).safeTransfer(to, amountToRedeem);

    emit Redeem(msg.sender, to, amountToRedeem);
  }

  /**
   * @dev Activates the cooldown period to unstake
   * - It can't be called if the user is not staking
   **/
  function cooldown() external override {
    require(balanceOf(msg.sender) != 0, "INVALID_BALANCE_ON_COOLDOWN");
    //solium-disable-next-line
    stakersCooldowns[msg.sender] = block.timestamp;

    emit Cooldown(msg.sender);
  }

The unstake window is 2 days after the cooldown completes. If you don't unstake during this time, you'll have to activate the cooldown again. link : https://twitter.com/AaveAave/status/1347250535087419402

My question 1: waiting for COOLDOWN_SECONDS to call redeem() is to make sure that users can not stake and redeem again and again in a short time. But why? What will happend if stake and redeem again and again in a short time.

My question 2: why design UNSTAKE_WINDOW? We need to call cooldown() ,wait for another time and must withdraw in UNSTAKE_WINDOW time. It costs more gas and it's not convenient for users. Maybe it is for security or the Business Logic of AAVE.