Everyone has an estate because everyone has assets - the money in your bank account, your retirement account, life insurance policy, stocks, vehicle, real property, your business, and all that other stuff you have in your apartment (tangible personal property). Plus you definitely need advance directives: living will, health care proxy and power of attorney.
If you have young children you need a Will. This is because minor children cannot inherit assets directly and you must designate a guardian to raise your children if you pass away prematurely.
If you have adult children and a spouse you need a Will. If you do not have a will, your grown children could inherit almost half of your estate instead of your spouse.