Aside from what others have mentioned, yes just the fact that you're getting paid makes a difference to the safety of the passengers. If you and your three fri

Aside from what others have mentioned, yes just the fact that you're getting paid makes a difference to the safety of the passengers. If you and your three friends have agreed to split the cost of a joyride on the weekend in your Cessna and there's an unexpected storm, you're much more likely to just cancel. You're all going for fun, nobody wants to fly in bad weather, and you can just go on some other weekend. Consider the same example where you have three paying customers who've you've agreed to fly around on the weekend. Now you'll be in a situation of having to refund tickets to disappointed customers. You might decide to go ahead with it anyway. Now you're putting members of the public at more risk for your own monetary interest.