Katisha - I wouldn't have an issue with a parent like you, and I actually wouldn't have expected you to remove your child from my group just because you weren't willing/able to get involved.
The thing is, though, all of this sort of group are run by 'parent-volunteers'. My DD (2.11) comes to my youth group and has since she was 3 weeks old, because it's take her or not run it - my DH is the other group leader and we both have to be there to guarantee at least two adults are!
I do it because I, in the main, enjoy it. So does my DH. But there are weeks where it's a nightmare, weeks when I don't do anything but plan the weeks' events and go to work and sleep. Running the group is my hobby, because it leaves me no time for anything else. It's not just 2 hours a week.
So, then, when I can do that, week on week for 6+ years, through pregnancy to 38 weeks, and be back with a three week old, unpaid for the time, effort and energy, why shouldn't I expect the other parents, the parents of the children benefitting form my time, effort and energy, to, once in a while, once a year or so, lend a hand to keep the activity that their child gets so much out of.
If I, if every other volunteer leader, stopped volunteering, then so many kids club type activities would vanish overnight. No-one is expecting you to run a session, but there are always ways you could chip in without ever being seen by the kids. In my group, for example, we run 7 or 8 sessions a year which run longer and are 'parties'. We put on a buffet for those nights - and that's the sort of thing where I need extra help. Preparing part or all of a buffet would be helping without organizing the kids.
Unfortunately, when I ask for help like that, I get a raft of 'too busy'. And my silent answer, behind my smile and 'that's okay' is : I'm busy too, you have one child and he's here, every week, enjoying and learning. I have one child and she's here, bored, every week so that I can be here for your kid. You have a full time job, I have a full time job. You have elderly parents, I have elderly parents. You want a night off with your DH - mine's over there. My life is no different to yours, and if you can be selfish, so can I, and then you'll have to entertain your own child.
My point behind the rant is that if parents want low-cost healthy activities for their kids (and they do!) then they need to be prepared to contribute in other ways. Otherwise, they are going to find that these groups go, and the costs of the things that replace them will be horrible, because they will be being run by people getting paid.