Why do i have a problem deleting dead people's contatcs.

I recorded my sister`s voice mail message when she passed. She sounds exactly like my Mom, also.
If I ever forget what they sounded like, I have a sample.
Its been 8 years for both of them and I haven`t listened to it yet, I`d probably start bawling...tearing up now.
My mom still has dads voice on her answering machine, I only let it ring 3 times when I call.
I miss my dad, but I have no desire hearing his voice, he is gone, but forever remembered.