Maybe gliding schools should provide a new appointments system or intensive course with some form of structure.
All of which is already available at the larger clubs.
Bookable training does not exempt you from helping to set up the launchpoint, or hangar packing. The nearest you will get to turning up & flying is to book a 1:1 session with an instructor who will do the legwork for you.
Clubs survive because having the members do the work keeps the costs down. Employing a host of staff to do the donkey work would make gliding prohibitively expensive.