This is such a great thread and its good to see differing views as it makes me think of how I was at first a guy invited to fish when i didn't have my own boat, to a guy who had a small boat to now having a new boat.
My first time being invited by someone was sitting at work and being asked if I could call in sick and go fishing on a week day. I said "no problem I'm the boss here right now so I can take the day off". We took his boat out and he paid all the fees I brought food, drinks and snacks. I didn't know anything about salmon fishing and he paid and covered all cost and had all the gear. On the way home I asked if I could pitch in and he said "thanks but no need for it" it was a small boat with a 50hp outboard so fuel used was very little. When he dropped me off I asked if I could help clean up. He told me he had his own routine so when he got out of the truck first I tucked a couple of bills in his center console for him to find later.... we have gone out fishing many times together on each other's boats since.
I had since been inviated out to other people's boats. Some I had met via a the internet through forums or FB groups. I always contribute something even if they won't take I will give them a lure that works for me or some other useful fishing item that I pre-pack so i can give it away. I also fished with someone out of another marina and he had a small whailer. He wouldn't take money either so I would hide cash somewhere in his boat or truck. Its become a bit of a game.
Later that year I bought my first boat 16ft double eagle with a newer 50hp Yamaha. taking people out on that boat did not cost very much so when I had friends and family onboard I didn't feel i needed them to share cost and often refused money as I enjoyed the company. It was nice to have them bring drinks/snacks.
My latest situation this year was that I had been fishing regularly with two friends I had met at my boat club. One I met via a work friend and I took one fishing for his first time on the ocean and put him on his first salmon on my little double eagle and wouldn't take anything when offered. He later got a Grady and had been taking out his boat more often then mine (as his was bigger and would handle windy/rougher days). He liked fishing with me because I was able to show him what I had learned and I a make a good crew. He also trust my fishing sense and usually asks me to figure out where we should fish. This worked fine for a bit but I started to feel it was a little uneven as we were taking out his boat a lot more then mine due to its size/fishablity and he still wouldn't take money for fuel/split cost so I made up for what I felt was the imbalance by buying things he needed for the boat and not taking any money back for it. For instance when I found a good source for lead balls/jigs/crab bait etc I would ask him if he wanted some gear as I was buying it anyway and wouldn't take money for it. He would expect to pay and I'd say something like "oh yeah lets figure it out later" and never bring it up again.
The other friend is someone both my buddy with the Grady met via our boat club. Older gentleman with a very large boat and is very well kitting out (Axiom MFD, Cannon iTroll riggers etc) who wanted some new fishing buddies as he was newly returned to the island. He also wanted to learn how to use his gear as it had all the bells and whistles and I happened to have some expertise from my work background. I ended up becoming a regular fishing buddy of his but once again he would not take any money as he seems to not have an issue with that. So for him I help him with work on the boat, teach him how to use his gear and when I fish with him I do a much of the physical work as I can as he is older. I tried give him lures etc but he buys them buy the case if he finds types he likes. He simply just enjoys having someone to fish with that "gets it" and knows what to do when the fish start biting.
I recently upgraded by boat from the 16ft double eagle to a 18ft (with 2ft pod) Silver Streak. Part of the reason (not the main one) was that I wanted to make it more of a fair rotation with my fishing buddies. When we go out I will not expect them to pitch in. I am fortunate enough to afford my boat and to run it so although I am happy to have guest I don't expect them to pay to come fishing. When I had a 50hp yamaha it used very little gas. The new boat doesn't use that much more being an aluminum.
I think circumstances really dictate if someone pitch in or not but its great to hear different perspectives.
. I've always said if you encounter "some asshole" every single day then you're the one that's probably the asshole.