There’s a lot of truth to this and I don’t disagree at all.I'll surely catch flack for this but here goes: I think there are 2 camps here. The renters and the owners.
Sure the owners would love to have some of the flight paid for. But in reality if you can afford to own you better be able to afford the full costs all on your own. Many people have offered to pay and my response is that I was going with or without them so please no money (@WannFly excluded!).
You are in the other camp, renting and watching your costs. I think its fair to ask them to cover part of it. But maybe don't shock them with the entire cost. Just say something like "I'm still renting and its kinda spendy how about pitching in $50 towards the fuel". And definitely use @SoCal RV Flyer advice you can literally tell them "I'll fly you buy" when it comes to lunch or dinner stop
But sometimes I go out of my way to make a flight nicer like flying circles over their house. Also, what would be an hour out of my day by myself is usually 3 hours with a guest, so paying some fuel costs to compensate for my going out of my way is appreciated. But I’ve never asked. It’s always a plus for me if offered. I’d be flying anyway after all.