Joe and I must have been typing at the same time, so there is some redundancy in our answers. I'll have to learn to type faster.
OK, I've already gone on record as saying in this case, I think the rope should have been loaned. But yes, it is not always a "black and white" answer. Here are a couple of the things that might lead to a "no" answer from a “good” person:
1) Liability concerns. Folks have some protection from "good Samaritan” laws, but some folks worry about liability more than others. Some worry about it A LOT! I loan you my jack, you use it wrong, car falls on you – in some cases, I could be held liable. So am I a bad person if you need a jack, and I won’t loan you mine? Maybe not; maybe I just know somebody that got sued for something like that in the past. Those who have studied a lot of river rescue reports have seen at least some where a rope caused trouble or made things worse. In one dramatic case on the Chattooga River many years ago, a rope was thrown to someone who had gone down into a pothole at Bull Sluice – a place where the water goes into the rock, and comes out somewhere downstream. The rope wrapped around the persons neck; they essentially hanged and almost decapitated the victim, who did not survive. If no rope had been thrown, the person would have flushed through and come up downstream. I heard the story from an eye witness; he was scarred for life by the memory and I assure you he felt differently about ropes and would-be rescuers than most of us.
2) Money. If I think maybe you don’t really, really need the rope – say, maybe I think there is not a life on the line, only a stranger’s boat, or maybe even a rental boat, then I have to think twice. Gear doesn’t usually get “destroyed”, which would almost always lead to an offer of like-for-like replacement. What happens more often is, it gets slightly worn or damaged. Maybe one end gets partially cut where it was tied to a boat; so my 75’ rescue rope has to get cut and suddenly I have a 70’ rope. Or maybe someone else walks all over it while it is in the sand. That causes damage we can’t even see, but the rope is now weaker. I’m not going to let you buy me a new rope for that kind of normal wear and tear. So I’m the one that will take the “hit”. If I go places every weekend, if I’m first in line to use my rope or hand it to others for every rescue, then my gear ends up with a very short life span.
You said you don’t use the rope much because you are not “trained”. I would encourage you to get a good river rescue book, read up a bit, and start using that rope. Training is great; I’m all for training, but I am also in favor of “experience” and “self study” and a big believer that formal training is only part of what should be going on. Don’t hold yourself back between now and the time that you get that formal training. You don’t need to have the formal training to toss a rope to someone in trouble; you can practice the throws in your yard; you can look at the diagrams in any rescue book and learn how to pick “good” and “bad” places to throw the rope from. Then when you go for your formal training, you’ll get more out of it because you will already have the basics down, and you can concentrate on picking up some new or more advanced tricks, instead of everything being completely new to you.