Sedburgh has got it spot on
As Sedburgh and many other people have written, the essence of most gliding clubs is that they are members clubs and the membership help each other out.
I tugged at the Norfolk Gliding Club for many years as a club member. I was not hour building and did not need to do the flying but did so (as a PPL holder) in order to help out my fellow members. Other members did the same when I was on the back of a tow in a glider. You will find plenty of people helping out at a gliding club whether its manning the launch control, driving the retrieve, holding a wing tip, attaching the cable, giving the up slack and all out etc. No one would suggest that these people should be paid/want to be paid or are getting some sort of taxable benefit in kind. Many clubs don't have the luxury of an aerotow and I can remember spending many cold and lonely hours manning the winch at the West Wales GC in the mid 70's. Should I have expected to get paid for that?