UFO is not your only enemy. Consider heart attack, car crash accident ...
With no backdoor, you can design your own password recovery procedures - password may be divided into parts and memorized by group of person (so you need three persons to recover it in full). Or it may be just written on paper and stored in safe. It's up to you.
With backdoor your policy can be overruled by an unauthorized person. You may lost control over your phone anytime.
