Reincarnation isn't actually a core tenet of Wicca. It's something that some Wiccans believe.
I've been Wiccan for over 20 years, and I do not believe in an afterlife. The gods have made it very clear that this life is important, so if there is an afterlife, it's not important, and there is no point in fretting over something that is both unimportant and not within our control.
We are told to observe the universe for answers to questions. When an apple falls from a dying apple tree and grows into a new tree, that takes the old one's place, is it the *same* apple tree it fell from? NO. We are a natural religion, why would we think otherwise?
As I have said in the past, fretting over an afterlife is like standing in the street, with a truck barreling down at 55mph, ready to hit you, and pausing to consider what you might have for breakfast tomorrow.
A good Wiccan knows that dealing with the truck (this life) is what matters, not something that may or may not happen, especially if we don't deal with this life.
Edit: I'd like to add that the mysteries regularly include references to afterlives that don't involve reincarnation at all as well...how literally you take them is your own matter. I tend to think they change things in this life, not the next.