That's not the point. If you were running a sight seeing operation for compensation, you'd be doing so under part 91 and your pilots would need a commercial pilot certificate, a 91.147 LOA, and a drug and alcohol program. You wouldn't need an air carrier certificate.
If you were transporting pizzas point to point for compensation, you would be doing so under part 135 and would need to hold an air carrier certificate and your pilots would need to hold the certificate appropriate for the part 135 operation.
My point is that Young Eagles flights are not analogous to the Kelly Island Pizza Pilot because if his operation was determined to be conducted for compensation, he would be violated for not holding an air carrier certificate. Conversely, someone doing a Young Eagles flight for compensation would only be violated for 91.147 and 61.113(a). Two different operations that must comply with two very different sets of regulations.