In my opinion there is genuine cost sharing between club pilots where often ppl’s share flying legs.
Yes, and perfectly legal to share the cost.
However rookie pilots with a new licence are hardly qualified to be flying the general public on sight seeing expeditions.
But does anyone really believe that PPL's don't get re-imbursed for flying "their friend" ? Maybe even "In kind", a reasonable car purchase deal, or "consideration" when subsequently employing a friendly tradesman ?
What is to stop a PPL hiring the club aircraft, paying for it, but then charging "the friend" for a cup of Nescafe brewed up in the club kitchen afterwards ? Not ethical, or approved by the CAA, but would that be "legal" ?