Fundraising for my salary

Location: UK
Job: Charity worker

I work for a charity and I don’t understand why we are constantly encouraged/forced to join in on fundraising activities in the office. I’m treated like an outcast when I object, which is ironic considering the cause we are supposed to be working for. I just don’t understand what the point is of me handing money back to my employer – are they paying me or am I paying them? I don’t want to take part in ‘forced fun’. Believe it or not, I have actual work to do. I spend more than enough of my time surrounded by people too worthy for their own good who think that tweeting anything with a hashtag is making the world a better place. I certainly don’t want to spend an hour crammed into a tiny meeting room with them eating their dry, tasteless cakes.