Charity rides are a way to get off the weaning of racing. That being, when you quit racing it's because you don't have it anymore, and usually get your rear handed to you more than once on your way out, and it's a shiitty feeling if there ever was one. So we wait a few years, get fat without really noticing how, and get back into riding by preparing for one of these things. It's still a crappy feeling when some older Fred in full USPS kit with matching Madone who obviously never raced in his life drops you, but you know in your heart you can go much deeper into oxygen debt than he ever did, and so it doesn't matter. Screw him.
Used to ride the Tour de Cure here, it was 10,000' of climbing total, after going up 6,000' on Mt. Hood. They ditched that course as being too tough, and moved it out to farm land. Rode a few more charities, but that was my favorite.
Keep saying I'm going to ride the Markleeville Death Ride (plus the extra punishment up super steep Pacific Grade) or the Mt. Shasta Challenge. But that takes serious dedication and weeks of training through the hills, and each year I get slower and creakier, and remember the day when I rode those roads in a 39x23 without too much difficulty, and it's a tough pill to swallow.
Club rides are often less grand or organized or fun than the charity rides. But they are cheaper and you get more comraderie and chatting. Plus it's less dangerous to wheelsuck (and believe me, I'm a real pro at this).