It's not necessary because of an external firing force. BitLocker is a bomb dropped by Microsoft onto Windows customers, and has countless absurd excuses for demanding an unknown recovery key at any moment. This includes changing the BIOS or UEFI firmware boot priority, inserting or removing an optical disc as part of normal use if the CD/DVD reader happens to be higher than the internal HDD in the boot priority, creating or resizing a partition, enabling or disabling firmware support for booting from USB, a firmware upgrade such as the automatic UEFI updates through Windows Update, inserting a wireless card into the computer, inserting a keyboard with a different layout, pressing F8 or F10 during startup, or using the single time firmware boot choice menu.