niknak (& others)
There's a clue into how gliding CLUBs operate. See if you can spot it in their name....
Booker Gliding CLUB
Lasham Gliding SOCIETY
Southdown Gliding CLUB
Kent Gliding CLUB
Derbyshire & Lancashire Gliding CLUB
Shalbourne Soaring SOCIETY
See, most of them are clubs and societies which are run for the benefit of the members and the sport a whole. They're NOT run as a commercial operation whose primary aim is to make profits for its shareholders. That said, they are run with a commercial element in that they don't want to run at a loss either.
To quote Niknak "as has been readily admitted, many gliding clubs make a good living"
Maybe they make a (small) profit but that isn't their primary objective - unlike airlines and commercial flying training organisations whose objective IS to make money.
If you want to go down the route of "hey they make a profit so they should pay the tuggies" (aside from the legal issue that PPL's can't fly for hire/reward) then why don't you start question why airlines expect pilots to pay for their own training in the first place ? After all, some airlines make heaps of money, so they can afford it can't they?
A fundemental point (which I'm sure I've pointed out in a previous, long lost, posting) is this: IT IS NOT MANDATORY FOR ALL PILOTS TO FLY A TUG FOR FREE. So, if you don't want to that's your choice, not a problem. Glider pilots don't sneak around the back of flying clubs coshing PPL's over the head and drag then screaming into the tugs. Equally, if you do like the idea of using the opportunity for learning more about a different aspect of aviation, taking part in a CLUB operation, enjoy the social side, and want to build some hours at no cost....then tugging could be for you.