Author must be reading different news articles. When I see "growing number of Americans will not be able to retire" I instead think "what happens when people become too old to work, have no money, but still need support to live?"
Broke -> Homeless -> Health Problems -> Abysmal long term care facility or hospice -> Dead.
A shocking percentage of the homeless people I see on the streets are very old. They are usually in terrible health and/or disabled. Social security minimums are no longer enough to cover rent, much less food and utilities. A lot of them are actively killing themselves with drugs and alcohol.
If you didn't get enough employment through your lifetime you can get checks for as little as $50/month. This is especially true of people who do a lot of under the table work like immigrants and people with criminal records.
Social Security, Supplemental Security Income, the Food Stamp Program, Medicare, Section 8, other state and local programs, the church and other charities, etc. And of course family.