The state will essentially decide what will happen with your assets. They will distribute them among family members and do the decision-making for themselves, making it completely out of your hands.
Do you want to be able to decide who gets your assets? Do you want to leave the people you love with what YOU want them to have? Would you be happy if an estranged relative ended up with your belongings?
This is why estate planning is so important. It allows you to choose where your assets will go while you are still living.