Yeah, people do. I've done some volunteering with my cosplays, and while I wasn't actually paid money for my time, it helped me land a sign-waving job for the grand opening of a dojo which did get me paid.
I say that because some people, though they may settle for free, are looking for that "compensation" in exposure and resume/portfolio-building. Granted, it's like going through rather than over an obstacle, but that ends up working to their benefit.
Even if you can't pay them directly, I'd actually suggest giving them something in return, like food/water if possible--it's "optional", I suppose, but it shows you actually do kinda care about them in the sense that you don't want them passing out. 'Course, this is something I'd do for strangers when conducting business of any sort, rather than friends and the like. If that makes any sense. ^^;