Oh my goodness.... I would be most upset if I felt pressured into doing charity work all the time.
Our guild does some, but it's only a small part of the guild, and there is absolutely no pressure to be involved. I do my own private "good will" things, and between that, running my household, squeezing in my own projects, and looking after our four children, I refuse to be pushed into doing anything else! LOL
Charity work can be a touchy subject, sometimes people don't feel able to stand up and say "hang on a minute, this is too much". Maybe it's time you did? You might be surprised, there may well be others who feel the same.