- Nixon was notoriously a klutz, and had trouble with technology in general. If he did the erasing of the tape, it shows—multiple stop-start attempts at erasure. At least one historian I've read (sorry I don't remember who) speculates that he started by erasing that tape, then gave up, overwhelmed by the task before him.
- Nixon wanted the tapes as insurance against others' versions of the events—at least until he realised how incriminating they were when thehe listened to them himself.
- Nixon wanted the tapes to record his legacy, and as the basis of his memoirs. He would not have proceeded to wholesale erasure of them.
- In fact, Nixon multiple times mused that he should destroy all the tapes. He never went ahead with it.