That’s a good way to put it. Part of the attraction of the fringe groups on both sides is that they claim to be fighting for something that’s relevant to the lives of those who join.
Volunteer EMS is a tough one. It’s hard to see how anyone would think that wasn’t a worthy cause, but as you said, in some areas the patients don’t appreciate the service. In our rural area it seemed to be the steady increase in training requirements that was discouraging volunteers. The rules are always well intentioned — who doesn’t want better-trained responders showing up to their emergency? — but if you push the quality vs. quantity equation too hard you end up with nobody answering the calls.
I think social media has made it easier for people to form groups based on common interests that have nothing to do with their local physical community. Legacy volunteer organizations are usually focused on their local communities. If you feel you have more in common with your Facebook friends than the folks on your street, you’re not going to be motivated to join a local organization.