Asperger's is a spectrum that spans long beyond where the random boundary towards an Asperger diagnosis is set. How dull life would be if everyone was on the totally "normal" end of the spectrum!!! Also "that" type of normal was frown upon less than 100 years ago, LOL.
So cherish your aspie traits!
I long ago stopped wondering WHY I lost interest in things and gained interest in new things. I just have fun with it. Although sometimes I can miss the feeling a certain interest gave me, but looking at that interest again I can't at all get into it.
I don't go way deep into things anymore cuz I don't have the energy and interests stay with me longer that a few weeks, still I know the feeling. Some interests cycle though and some never fully leave even if they might stay in the background.
I can't fathom living and have no interests, no curiosity. Sometimes losing interest can be a bit of a bother or a loss, but I have realized I can't make myself interested of uninterested.