Ryanair is a company, which aims to make a profit. All the employees are paid - flight crew, managers, engineers etc. What is left over goes to the shareholders.
A gliding club does not aim to make a profit (at least none that I have ever dealt with!). None of the workers are paid - instructors, the man who drives the tractor and the wife who makes the tea all give their time for free. The tug pilot is a club member just like all the rest.
I would feel like a complete idiot if I joined the club and demanded to be paid for towing.
Skydiving is different as often they are companies aiming to make a profit. The tandem master is paid, the receptionist is paid and what's left goes to the owner. In this situation the pilot should be paid as well.
So look around you - if your colleagues are paid then you should be paid too. If they are all volunteers, then you should expect to be a volunteer.
Just follow one simple rule - if the boss has a business card, then you should be paid
