Some people often think that because they don't own or have much, they don't need a will. Everyone needs a will if only to appoint an Executor and to state what you want to happen with your body after you're gone.
Without an Executor, who will arrange your funeral or burial/cremation or arrange for the donation to science? Your will would clarify what you define as science as an Executor would need that direction.
Likewise, someone needs to file your final tax return and notify the government of your death. If you don't arrange an Executor while you are alive, it creates a big mess after you're gone as that responsibility does not necessarily automatically fall to your next of kin.
Many rely on their spouse to carry-out their wishes. Consider that spouses are often together and if involved in a serious car wreck, a surviving spouse maybe incapacitated and not able to act as Executor for their deceased partner.