Perhaps in the hyper inflated SV economy, but in the rest of the world you don't get to retire until you've reached the normal retirement age (minus a few years perhaps), and that makes it quite natural to see newly employed software engineers who are in their mid or even late 50s. I've worked with plenty of them.
I must admit though that I've only seen one newly hired in their 60s, but probably the very few that find themselves involuntarily out of a job at that age can afford to and choose to retire a little bit earlier than planned.
Once you get into late 50s/60s, I know quite a few people in tech at that point who have had reasonably well-paying jobs (though certainly not top-level FAANG salaries) who have presumably managed their finances well who are pretty much ready to wind down at that point--whether forced or otherwise. They mostly haven't classically retired but they're working part-time on often IT-adjacent types of projects.
I must admit though that I've only seen one newly hired in their 60s, but probably the very few that find themselves involuntarily out of a job at that age can afford to and choose to retire a little bit earlier than planned.