I'll come to young Lister's defence on this one. I'd be inclined to take perfect strangers up (and, in fact, have done so when I thought it was possible to convert them from a fence sentry into a PPL), but that's after sizing the person up a bit and having a bit of a chat. It would also depend on how the person asked. I probably wouldn't charge for it as I look at it as part of the aviation ambassadorial role we all share, but I might take a few quid for fuel if offered. You do have to be a bit careful with people you don't really know, if for no other reason then to try to understand how they're likely to react once in the air. Are they prone to motion sickness? Are they nervous generally?
Also, there is the issue of the profit-making side of things. How touchy is the main operator about taking up someone who might easily be a paying trial lesson? That's not been a problem at the two main bases I've been at, but I could see how it might be sensitive at some.
On the other side of the coin, I've recently checked out in the Pitts S-2B and can't wait to take up passengers! Inviting people for a ride, especially if it's kind of a one-off, is a bit like a date. I'd expect to cover the cost as I'm the one that did the inviting. They can pick up lunch or the teas or whatever. If it became a regular thing, then we'd talk about sharing costs.
I think Lister was showing a bit of real-world prudence.
As always, justmy view. Your mileage (or endurance) may vary.
Pitts2112