Interesting...
Here in Europe, a common "scheme" seems to be that a PPL embarks on a VFR flight, but carries a passenger in the RHS who has an IR, and this enables them to request an IFR clearance should they need one due to weather etc.
I always thought this was dodgy unless the passenger was provided for by the insurance (e.g. named on the policy) because the evidence trail is clearly present (ATC tapes) on who was PIC, so if there was a prang on landing, the LHS would cross his fingers and hope that nobody pulls the tapes...
Whereas if you just let a passenger fly the plane for a bit (which frankly everybody does, sometimes) there is no evidence trail.
More importantly, in the event of a prang in which everybody but the said passenger gets killed, the passenger does not have a financial incentive to admitting that he was effectively PIC after all, and this is vital because people will make up all kinds of stories if they can get a bigger personal injury payout, and under the UK Civil Aviation Act passenger liability hangs on the establishment of pilot negligence.