Hi Tim.
Joining ACA is optional. It is a good organization for paddlers and they do a lot on our behalf. You can learn more about them here.
If you're not an ACA member, a $5 fee is required to participate in HCC paddle events. That's to cover the insurance for the trip. If anyone can't afford it, I'll pay it for them.
There is a liability issue, as drownings do happen, and one lawsuit could end the club. HCC has never had a fatality, but you can certainly read about a lot of them in the news. ACA membership provides liability insurance to protect us against that. Participants are asked to sign the waiver as protection against such lawsuits, stating that they understand the risks and choose to participate anyway. Many high risk sports do this, such as skydiving, horse riding, and such. It's a necessary feature in our law-suit happy society.
Bicycling, running and photography don't seem to have state and national issues like rivers associated with them. Those are more local issues, where city & county governments are needed to build bike and hike trails out of traffic. Bicycling can certainly be dangerous, so I'm surprised that bike events don't require a signed liability waiver. Paddlers need clout at the national level to stop things like dams from being built on our rivers, which can flow through multiple states.
The $5 fee is just the cost of a cheeseburger. Trivial! It's a lot of work for the trip organizers who have to report to ACA how many paddlers participated, send the money, and more. Just ask Kent who has to deal with all that. Compared to the hassle for trip leaders, the signed waiver and $5 fee paid by the participants is quick and easy. Yeah, no one likes it, but it is necessary.
We could withdraw from ACA, but then we would lose stature by not being associated with them, and we would be negligent in not participating and doing our share for the preservation of paddlers rights nationwide.