People generally have fewer financial obligations as they get older. A home mortgage might be paid off or nearly paid off; the expense of raising children and putting them through college may no longer be a factor.
In addition, you may have a substantial amount in your retirement savings.
So, is life insurance for seniors necessary? Maybe yes, maybe no, although life insurance at any age can be important. You might not need the same level of life insurance as when you were younger, but the risk of not having life insurance may still be greater than the cost of having it. A lot depends on how many loved ones are dependent on you and how much of a safety net you already have.