If the couple you're pillorying is so wealthy, then most of their Social Security is being taxed, and they're paying higher Medicare premiums as well. And their house? As they get older and require nursing care, they'll end up liquidating it (or Medicaid will take it).
The average retiree receives around $25k per year in SS benefits. That's not a ton of money. In most studies, retirees receive less in benefits than if they had been able to invest their Social Security contributions. But that's fine, SS really has two main goals: a forced savings towards retirement, and as a social safety net for those who would otherwise be impoverished in old age.