Doesn't have to. With some empathy you can often tell. Also don't need to know anything to know that 70+ year olds don't work at some menial service industry job in countries where they can afford to retire.
>He loves driving the bus, he does this to stay busy, he's retired but enjoys having a purpose and talking to people (such as myself). My point is you have absolutely no idea why anyone does anything, unless you ask them.
That would tell you even less in many cases. I wouldn't necessarily believe the story a stranger would present for their circumstances either. Part of it will probably be saving safe, or making himself look better than "70-something that can't afford to retire and is forced to drive around".
The fact is, loving it or not, he probably works because he 100% needs the money. So a health incident, or some emergency (like his house needing repairs, or a rent hike) could wipe him out.