IFMU, yes, but if there were no paid duties/roles even in non-profit clubs, in true American fashion, not much would get done/people airborne. Yes, there are few 'volunteer/unpaid instructors/tuggies/duty pilots associations' in US, but not the same.
I love power flying in the US and have done some gliding, but I like UK club scene more in comparison.
The amount of 'ground crewing' really depends on the amount of flights, whether training or check flights, solo pilots launching, aerotows vs winches, amount of trial lessons that morning/day.
The owner pilots assemble/preflight their glider themselves, can tow out the glider with car to launch point, need quick hook up and running wing and they're gone. So it's more ground chores for winch ops, cable break practice flights (landing ahead means buggy/car towing back), trial flights.
VJ, you basically aren't going to have issues getting solo, from your further posts. I don't think you can 'book good soaring conditions time slot' unless it's one of the mentioned clubs and it's summer season/good forecast.
If you're cash rich time poor, generally don't bother with pure gliding in small/smaller 'volunteer' club. There's a lot of delays and setbacks/disappointments and high attrition rate of trainees/early solo pilots as it is. Gliding's great, by all means, just not for everyone or nor for too long. The least stressful kind of flying besides other pure soaring.