The problem is that future actions are not under your control - they are under the control of the person (or family) of the person treated and you don't know, in advance, what they are going to do. It's only prudent to know how to protect yourself, as best you can, against financial risk.
And before you say that there should be a law that prevents someone from suing, there have been a significant number of cases where an untrained first responder caused permanent injury, including paralysis or death, because they didn't know what they were doing. Good intentions are cold comfort to the person or family injured.
So we have courts to decide whether what the person who responded did was reasonable or not. The courts usually give lots of leeway to the responder, however.
Go into the world and do well. But more importantly, go into the world and do good.