The discussion is "want to work" vs. "have to work." There are plenty of people with no interest in retiring but there are even more who don't have the financial wherewithal to do so. Social Security doesn't cover the expenses for a lot of people (despite being a quarter of the budget). That number is growing.
There will be people who are happy being a Walmart greeter into their 80s - after all, your job is to say hi to people and act friendly. But there will be more who weren't into what they were doing before they were forced out at 68 and now they're finding out who wants fries with that to make ends meet.
Until the robots come, anyway.