Yeah, what's that saying about Discretion is the main part of Valor? Or, to put it into country terms, my Mamaw told me that you don't gotta say everything you think. You made a wise choice by not engaging in that discussion.
More to the point:
Remember, though, that he may not've been completely honest with you. Perhaps he's perfectly able to retire but is staying for other reasons. I doubt he's unable to afford private health insurance, but it might be that his identity comes from his job, and if he were to quit . . . he'd feel like he's nothing. I'm thinking of a man I know only in passing, a man whom I'm certain has millions upon millions; he'll work 'til the day he dies because he has nothing but his work. If he were to get sick and be unable to work, he would probably die. Literally. Or perhaps your guy is pretty well happy working, but was having a bad day. Or it could be any number of other reasons.
I can tell you that I am perfectly able to retire right now, but -- for several reasons -- it's better for me to stay employed for a couple more years. Knowing that I can walk out anytime I wish makes it pretty easy to come to work every day. Also, even though I like my job 90% of the time, that 10% is quite real. I wish I didn't have to come in so early every day, and I have a couple tasks I'd rather not do -- but are they enough to make me leave, given that staying a couple more years will make me inflation-proof and give me a few other benefits? Nope.
But then, I also don't go around complaining about working.