A PPL holder doing a grey charter is no way trained and rarely capable of handling what can be thrown at them.
Not trying to defend grey charters but I think there are probably many highly experienced pilots who fly very safely but who have never needed a CPL because they don’t want to earn money from flying.
If I take three people I don’t know for a flight in my aircraft, for example flying veterans and their helpers to Project Propeller, and don’t charge them, that is deemed to be legal and, by implication, to offer an acceptable level of safety. If I charge them for the flight illegally, it doesn’t change the level of the danger they face even though I would be committing an offence.