I believe the original point was that taking friends flying with a basic PPL is legal, but if they pay more than their share it becomes illegal, and that this is illogical. Yes, it is.
No, not illogical (at least, to my mind), Whirly.
A line needs to be drawn somewhere. If the pax pay their share, then it's just a joint jolly. If they pay all the costs (plus a "drink" for the pilot), then it becomes indistinguishable from a charter. So where do you draw the line? It's reasonable if two business associates are going off to a distant meeting, one has a PPL and decides he's going to fly. His colleague decides to come too, and offers to share the cost. Nobody is benefitting. But there comes a grey area in the middle. How much more than "his share" can he pay without it being a charter? Somewhere, I would suggest, between £(Cost/2)+1 and £(Cost-1). The line is, I suggest, therefore logically in the right place.
Public transport needs to be subject to oversight and therefore legislation and licensing, for the public's safety and financial safeguards against operators going bust. Hence the requirements for AOCs and ATOLs. Hence the higher requirements of licensing and recurrent checking and medicals for pilots conducting such flights.
Not only do the public need to be protected against the wiles of the pirates illegal public transport operators. So do legitimate businesses who incur significant costs in ensuring their aircraft are suitably maintained, pilots are trained, checked and medicalled (??), their duty hours within safe and legal limits and the whole caboosh is insured.
Therefore like, I suspect, a lot of commercially-qualified pilots, I would have no hesitation whatsoever in shopping anyone conducting illegal public transport.