I just think who can give the damn things a happier life than me and the family.When you get older and your children are adults, any pet becomes like a replacement child...yet our children aren't supposed to die before us. That's too painful for humans to cope with. It's that instinct of looking after them..
It's painful when they go but the joy and memories they bring is enough for me (hence the reason I've got an 18 year old cat who refuses to die! And a black lab).