actually they just give in to gravity and the fact their holders don't want them anymore. i don't think there's much space for a romantic interpretation in that.
i am going to be engeener, so u don't have to explain me the laws of physic. but there is one saying "someone" important said "imagination is more vulnerable than knowledge", about whom u germans should know the most. If you just see leafs falling because of gravity u see an object, an obsticle, if you look deeper u try to wonder and see something else, a sparkle that can change the world ;) and don't be so negative
but if leafs were human beings, they would try to resist falling. there must be a reason why they fall with such grace and beauty.... they have to belive in something :)