The Mountaineers climbing program centers on teaching. Most people who climb with the Mounties take the courses, then teach and lead climbs to support the courses. Those who don't teach and lead after graduating typically don't continue to climb with the club, i.e., on official club climbs.
However, graduates of the courses, whether they continue to help run the program/classes or not, often meet people to climb with--fellow students, climb leaders, mentors. "Unofficial Mountaineers climbs"--climbs in which all the participants are members but the climb isn't registered as a club climb, and so it's actually a private climb--are common.
But my sense, being a member since the early 90s, when I joined to take the Basic Climbing Course and work on the fire lookouts, is that very few climbers stay active *in* the club if they choose not to, or tire from, teaching and leading. There's been a couple of generations of climbers and leaders since I took the course, and the only ones that I know of that go on club climbs are the few who still teach and lead climbs to support the courses.
It's also hard to get equivalency status (permission to participate in club climbs without going through the courses)--another reason that non-course-related climbing is not a big activity in the club.
The club has been looking at keeping and building membership the last few years--maybe they should consider this.