>I cannot see why an atheist would do this.

Because an atheist is typically a quesitoning... "what if" kind of person.

When faced with life, and given the question about death and afterlife, an atheist may say "what if there is no afterlife? what if this is what we have and this is what we have to take advantage of?"

When faced with death, they may say "what if the memory of me has a life of its own after mine? what if my memory does not look happily on my happy life?"

All he wished is that his memory portrary him favorably. I don't think from your quote he really is saying "I wish I wasn't selfish in life" but more "I hope I was also a caring person, and that this is the side of me people remember."

I imagine as I face death I'll sympathize rather well with such sentiments, though I'm not exactly an atheist as much as I'm a deist, but they are not mutally exclusive in my opinion.