I must say I am rather surprised at how busy some gliding airfields can get.
Some years ago, Farnborough were making a case for airspace and did a survey of other local users. They happened to pick the week of a competition at Lasham when 100 gliders were launched in a 1 hour window, over 300 movements/hour. (Each launch = 1 glider take off, 1 tug take off, 1 tug landing). It's not always as busy as that, but on a good soaring day can get close. A good lookout is emphasised all through training (and on currency checks).