I haven't made it all the way through this thread, as I'm getting ready to leave for an appointment. I do plan to come back and read it later this evening, as I find this interesting and have asked this question, myself. I did have a thought and wanted to relate it, and I apologize if I'm repeating something that someone else has said.
Why do we remember past lives? I have two thoughts.
First, in young children, I believe it's because their most recent life is still "fresh" to them and rather than feeling like something "long ago and far away," those memories probably feel to them, like our own (current life) memories from last week, last month, and last year.
Which brings me to the second thought:
Why do we remember specific memories from our current incarnations??? For me it is triggers: smell or taste, a scene or event, a song, etc.
There is no way I could sit here and recall my current life's memories in great detail from beginning to end. Even when remembering a specific event, I may not remember every detail. Sometimes I will talk with a loved one about "remember when ..." and relate what I'm thinking. Then they say, "Oh yeah! And remember that such and such thing that happened?" and up until that "prompt," that particular memory wasn't in my thoughts.
OR
I may have a trigger that prompts a specific memory but leaves out some forgotten detail until a future prompt triggers that detail for me, as my previous exampled loved one did.
Sorry if that's a repeat of anything anyone else has said. I just wanted to get it out of my head before it left forever.