But you CAN get a PPL and do pretty much what a CPL holder does; you just can't be paid for it. That's the whole point.
With the greatest of respect Whirly, no it's not the whole point.
A PPL holder is tested to a far lower level of competence than a CPL or ATPL holder. He does not have a mound of regulation with which to comply (He may think he does, but, until he's got an AOC, as the saying goes, you ain't seen nothin' yet).
A commercial operation needs approved post-holders in certain jobs. Those post-holders are approved by the CAA based upon their experience. The Ops Manual has to be approved, and relevant to the type of operation undertaken. The aircraft has to be maintained by an approved organisation, not just Joe in the hangar at Lesser Snodgrass airfield. Pilots have to be subject to a satisfactory Duty Hours Limitations scheme. None of these are of any relevance to a PPL holder taking a back-hander for taking his boss off to a meeting or running a package to the factory at the other end of the country or even to "here - buy yourself a drink or ten" for taking people up pleasure flying.
The argument about carrying pax or goods is irrelevant. Protection of the public is the point, whether it's protection from injury or death or, depending on the nature of the package, financial damage (or ruin).
I worked f***ing hard for my ATPL's, IR's and instructor ratings. I paid a lot for them. I have now EARNED the right to be paid to fly. I am a professional pilot, and give a professional service, whether taking people up for a 30-minute jolly in a PA28 or flying them across Europe in a BE200. They can be confident that my hours are subject to statutory limitations. They can be confident that my company keeps track of my medical due date and any recurrent training and checking. They can be confident that I have been trained to a sufficent level that I can single-handedly carry out a procedural NDB approach in crappy weather down to minima with one engine failed, a go-around and diversion. They can be confident that I've been trained (and retrained) in CRM regularly. They can be confident that I have the minimum number of hours for the job as specified by my employers.
What can they be confident of in a PPL?