Do I really need my bootloader unlocked?

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http://forum.xda-developers.com – Im not such a fan of custom roms or custom kernels. I always stay on Stock roms, I dont really like to mess around with my phone other then rooting it and i also like to replace system apps from other phones I previously had, so I usually make nandroid backups if something goes wrong I just go back to a previous working backup. So my quetion is guys... Do I really need to unlock my bootloader? If I brick my phone and need to reflash my stock rom do I need to have it unlocked? Or what would be another way of getting it back to life? Oh and finaly can I have CWM without been unlocked? Please (HowTos)