Travolta owns a 707 passenger jet. There aren't many private pilots with aircraft this large.
So you do actually know that private pilots can and do fly "large iron", and your presumed limitation to "50-year-old Cessnas" and 4 seats was fictional.
I'm sorry, I don't spy on my neighbors and relatives enough to know how they maintain their cars.
And I said no such thing. I said you have "some indication". You are probably going to know if Uncle Bob has gotten his fourth DUI and his license is suspended, and even if you don't you'll probably know that Uncle Bob is a lush who is lax in following the law. You have NO such clue about that taxi or "ride-share" driver who just pulled up. If Uncle Bob gets into a wreck with you in the car, you're probably going to know where to find him when you sue for damages, and even if he moves, someone in the family will probably know. That cabbie -- you don't know where he lives, and you may not even know his name. (The one time I was in a cab wreck -- he ran a yellow and got t-boned -- I have no idea who the cabbie was or what company.)
In any case, Uncle Bob isn't giving you a ride to make money so he's got no incentive to give you a ride despite mechanical troubles with the car, where that taxi driver has a boss who likely will tell him to keep driving and his hack will be fixed next week, maybe, if there is a problem.
If you think the majority of private pilots are flying King Airs, or anything made in the past 5 or 10 years, then you're a complete moron.
And I said no such thing yet again. It doesn't matter what the majority of private pilots fly, it has to do with what ALL of them are AUTHORIZED to fly. Yes, I need to have a multi-engine license to fly a multi-engine aircraft, but just a logbook signoff for complex and high-performance. And I'm still just a private pilot after getting all of that. I still can't charge anyone for my pilot services, even just one.
The number of passengers, contrary to what you write, is a huge point.
You are simply wrong. There is nothing in the FAR for private pilots that limits the number of passengers. Nothing. John Travolta doesn't have to say "I can only fly four of you" because there is some "four passenger limit" on his license. The differentiation between "private" and "commercial" is pretty clear from the name -- "commercial" is done "for compensation", and it has nothing to do with how many people are involved. A pilot who charges just one person for a ride needs to be operating under a commercial license.
There ARE no standards at all in most states. If you disagree, then you are woefully ignorant.
I know of no state that issues driver's licenses without any kind of test, nor do I know of any state that does not have some standards as to mechanical function of licenseable vehicles. My state does not have mandatory inspections (although the Portland/Metro area does), but it does require testing to get a license in the first place. While it doesn't require much for a renewal, that is a FAR cry from "no standards".