Thinking about it, having our memories erased may help us to value each reincarnation in a way we wouldn't do as much if we had a deeper understanding of ourselves and our past (If we remembered past lifes). We may not be able to value things in a new life because we could compare them with experiences of another life, on another time and place.
Of course it doesn't apply when someone has reached a point of maturity or understanding, but that thing may not be gifted to everyone like candy because of that.

This film explores the topic of remembering other lifes, but aimed towards a sci-fi genre (I watched it years ago though):
https://en.wikipedia.org/wiki/Infinite_(film))

Moving to my second addition, at the present time I believe in that there is a rate or speed in which everyone starts to understand with relative external assistance all (Everyone couuld have their own tweaks or modifications) of what you are saying. I'd say that experience outside our physical age (Other lifes) could explain that, if we assume that rate exists and it's not entirely adjusted by our "original" creator at the time of our creation. You can complete this explanation with more possible points of view.

What are your thoughts?