When you are in your 20s, you are just starting your career. While you may not have many assets, you still should have insurance to protect you in case of disability.
During your 30s, 40s, or 50s, you will likely be juggling a mortgage and working toward paying for college for your kids. During this time, you should have a policy that will pay enough to replace your income if something happens.
Later on, in your 50s or 60s, your children will likely be independent, but, it will be time to think of taking care of your parents. Life insurance can make sure that they are cared for if something happens to you.
Then, it is time to think of your legacy. Life insurance can allow you to leave something for your family.