Do people mocking volunteers honestly think that Olympics and Winter Olympics held in other countries are any different. THEY ALL rely on volunteers, they can't be paying every single person involved, that would be ridiculous.
One other aspect, which isn't so prevalent in the UK is that many employers overseas expect to you to have done some volunteering work. I know that was the case when I made CVs when working in Canada, as employers wanted to see that you had done some.
Although it's not so important here, it's never a bad thing to have on your resume.
At the end of the day, you don't get paid, but will get some perks for doing so and being part of Olympic history.