[True enough, but for lack of desire or lack of invitation?]

Possible, though perhaps not entirely for that reason. The gaps in my own memory are haphazard enough that I find it difficult to imagine them all being related to providing me a motive.

[Besides, he can't see his motive changing for much.]

It seems more likely. At least in my own world, it's quite difficult to truly destroy a memory permanently. Far easier and less work to suppress them.