Let's get semantics out of the way: if you accept payment to drive somebody, and you have an agreement that they will pay you in exchange for the ride, that is just like Uber.
Here is the definition: an agreement, including implied agreement, to provide a good or service in exchange for payment.
OK, I carpool with a co-worker, and every few days he drops $10 on the seat, or buys me lunch for the wear and tear on my car and gas consumption.
No agreement has ever been discussed, even implied, at all, ever. He just started doing it because he is a stand-up guy. Is that a "commercial transaction"?
PS: I like how you ignored the double-double analogy.

