To get a licence to drive a minicab in the UK, one must have held a UK/EU driving licence for at least 12 months. The 12 month threshold is there so that while someone my have passed their driving test and legally qualified to drive a car, they will almost certainly have spent a year driving around and building up experience (e.g. handling heavy traffic, busy roundabouts, motorways, driving at night, etc) before they are let loose on people who have no knowledge on their competence.
If I'm in a car with someone who I think is driving dangerously I can at the very worst case ask them to pull over within 30 seconds and get out the car. As a passenger in the front seat, if they refuse to stop the car, I can even pull the hand brake and force the car to a stop if I absolutely have to
When you're in a plane up in the air, there is no "please pull over within 30 seconds and let me get out" option, particularly when flying cross-country rather than circuit bashing around a home base. Someone with low hours necessarily has a low level of experience and may be more than a little challenged by what to do when something surprising happens. As soon as money is involved, it becomes much more embarassing to ask another pilot whether going up today is a good idea or not - and a desire to avoid looking silly becomes a decision to fly anyway.
Yes, Wingly has the option for passengers to give ratings on pilots. I can rate hotels as well - but even if the hotel room I stay in has cockroaches it's unlikely to present genuine safety issues. There is also usually back up from a local Govt inspector to ensure that things like fire escapes are properly maintained.
However most passengers on Wingly will rate mainly on "seemed like a nice friendly person" - passengers generally are unable to determine a level of technical competence and safety. Wingly seem to be encouraging passengers to decide on whether to fly based on other passenger ratings - i.e. decide solely on whether pilot "seems like a nice friendly person" rather than safe and technically competent
Yes, once you have your PPL you are legally qualified to take someone for a trip and for said person to pay their share of fuel costs. I think people are focussing rather too much on what they are maybe legally entitled to do - one must also be responsible and ask "Is this really a good idea ?"