We don't have regular competitions at our club (Mid Wales), but we do have an active group of contributors and our members' work table often draws favourable comments from demonstrators, but as with your club, it tends to be mainly committee members who contribute. In our case, I'm guessing that as much as 60% to 70% of the work is regularly that of the committee. However, that's n ot really surprising, after all, if you are committed to turning and to the club that you join, then it follows that there's a strong possibility that you'll also be a contributor to displays of work and to serving on the committee.
Les