I think all 3 of those main reasons you listed have merit, and ultimately it comes down to just being respectful.
This, don't be "that guy". You know, the guy who shows to a potluck with no food or doesn't offer gas money on a road trip or doesn't tip at a restraunt. Pay your fee like a grown up and enjoy the race.
I think respect is subjective. I think it's pretty disrespectful of race organizers to use volunteers to widen their profit margins. But that's just me. There's actually a lawsuit going on about that. I don't personally think it's valid, but it brings up an interesting point.
Your arguments feel like they're just based on what people around you think is right and wrong, and you've just adopted their belief system. Nothing wrong with that, it just doesn't make for a strong moral argument.
What if a guy that shows up to a pot luck, but doesn't eat anything? What if a guy who is invited to a pot luck, tells the organizers he's not going to come because he's not bring anything, and is told to come anyway?
I would say stop going on road trips with people who aren't going to pay up....or if you offer to drive then be good on your offer and eat the cost. Again this is a cultural expectation, not really a moral one. For instance, in Japan, the layers of cultural expectation are through the roof. If someone turns down your invitation to hang out, you're culturally required to make up an excuse for them so they don't have to be burdened with that task.
Do you tip more for a good waiter or a bad waiter?