Understanding Why

Everyone always says "You'll understand when your older." But when is older. When is the point where it starts to make sense. When is the point I feel wanted. When will I have a home? When?
You'll never really know why your parents leave you. You'll never know why they just stopped caring. You just feel unwanted. When I was a baby my parents left me on the steps of an home for girls. My foster mother only told me what there was to know.
I was in a basket. There was a necklace that said "Luna" on it, and that is it. Nothing more. Why didn't they leave a note saying why. Why didn't they stay with me until they couldn't. I always wanted to know why they left me. My foster mom is Eva. She was the nicest person I have ever met. She is a good mom, yet she never had kids of her own.
We live in a small town. There is only six girls living with me. There was more, but they found homes. Me, well no one wants me, and I don't know why..