Without a clear will and stated wishes, the decision of who cares for children becomes exponentially more difficult for surviving family members, leading to disagreement among parents, siblings, and potentially state involvement.
"As hard as that decision is to have while you guys are still on this Earth it becomes exponentially more difficult to have if you're not here to speak on behalf of what your wishes are because then you leave the family guessing well I think my parents are going to be well my parents are older and then your sibling says well no no it should be us cuz the cousin"