GBS
With great respect, what you describe in your last post is very far from how these cost sharing flights work.
Certainly when I used to offer them, I always made it clear to riders as soon as they asked to join me on a flight that it was subject to change or cancellation, either due to weather or even just because my plans might change.
I wrote an account of the way I used to handle this in my earlier post in this thread and would encourage you to read it, as it addresses all of the points you make here. I will say that the grand total of commercial pressure I faced when I did decide to cancel or reschedule a flight was precisely zero.
The simple fact is that cost sharing flights are legal and have been going on legally since well before ride sharing sites had ever been heard of; and under CAA and EASA (both organisations not exactly famous for their flexibility in enforcing licensing regs!), arranging them using Skyuber or Wingly is legal as well.
If you think cost sharing flights should be banned because they are in some way less safe than a flight with no cost sharing: that's an opinion to which you are entitled, and I suggest you lobby the CAA / EASA for a change in the rules.
The suggestion that somehow these ride sharing sites are spawning a mass of phoney charter operations is simply not supported by the facts.
AFAIK, someone has identified a single naive pilot who posted an ad that he shouldn't have done. That's very far from the nightmare you seem to be having about this.
That said: if anyone really does seriously try to sell phoney charters, whatever the medium they use to do so: they should have the book thrown at them, and I doubt it would take very long for that to happen. That is because it is also against the interests of the sites to allow such ads as they would probably also be liable to prosecution for promoting an illegal charter.