Two retired people collecting Social Security are getting two checks. When one of them dies, the survivor keeps the larger of the two, and the smaller one stops. The household does not keep both checks, and the two do not get blended into one bigger payment. The survivor keeps the bigger check, and that's the household income from then on.
Run your own numbers on that. Say one spouse gets $2,600 a month and the other gets $1,400. The household is living on $4,000 and drops to $2,600. A third of the income is gone. The property tax bill didn't change, and the Medicare premium is still coming out. Households where the two checks are close together lose less. Households where one person earned most of the money lose more.
The survivor benefit has its own timing rules, and they aren't the same as the retirement rules. A widow or widower can claim as early as 60, or 50 if disabled. At 60 the benefit is cut to 71.5% of what the person who died was getting. Wait until your own full retirement age, which is 67 for anyone born in 1960 or later, and you get 100% of it. Waiting past that does nothing at all. Survivor benefits don't earn the credits that make a retirement check grow, so there's no reason to sit on one past your full retirement age.
There's a rule called deemed filing that normally forces you to take every benefit you're eligible for at the same time. It doesn't apply to survivor benefits. So a widow can take the survivor benefit at 60 and leave her own retirement benefit alone, letting it grow 8% a year between 67 and 70. Then she switches to her own at 70 if it has grown larger. Or she runs it the other way, if her own is the smaller one. Two benefits, and you get to pick the order.
Which makes the higher earner's claiming decision a joint decision instead of a personal one. Waiting until 70 adds those 8% credits to the check, and the credits carry into the survivor benefit. They keep getting paid for as long as the survivor lives. Claiming early at 62 locks in a permanently smaller check across two lifetimes rather than one. The tradeoffs on timing are in claiming Social Security at 62, 67, or 70.
Social Security also pays a one-time death payment of $255 to the surviving spouse. The $255 is the entire funeral benefit. The amount hasn't been raised since 1954, and today it doesn't cover the flowers.
So the gap to plan around is the smaller check, times twelve, times however many years the survivor is likely to outlive the other. Life insurance is one way to fill it. An annuity with a survivor option is another. A pension election with a survivor benefit is a third, when there's a pension in the picture. Pull both benefit estimates from your ssa.gov accounts and work out which check disappears first, because the answer sets the size of the hole you're covering. The same calculation is laid out in what a free needs analysis actually is.