Ask HN: Where do older workers go that don't become managers or specialists?

I really enjoyed the recent Ask HR post on this topic (https://news.ycombinator.com/item?id=7372997) but since it is locked and I can't comment, I decided to start this one to ask a very specific question. Yes, I understand that the most common paths for older workers are either management or senior roles, but given that the number of these roles is a fairly small percentage of the total workforce, I want to know where the REST of these older workers go? Do people really retire that early -- and if so, how? Are they all working as greeters at Walmart? (if so, please shoot me now)