While those interests may overlap, the diversity adds a range of differing activities. These diverse activities also attract a wider range of people and thus more members. It also eases the task of those members who do most of the trip sponsoring. I like certain activities but don't feel comfortable leading an outing. Bring up your idea at a meeting and ask if someone will co-sponsor the event with you or ask the Events Coordinator to sponsor it.
Every outing needs one designated person to attend that outing, and usually it's the sponsor.
If the Events Coordinator is sponsoring an event for you, it is still your responsibility to be in attendance. Nothing is more discouraging than to have someone bring an idea to the meetings, encourage people to attend, publish a date, and not show. I want to attend an activity in the newsletter. Call the sponsor listed in the newsletter article. Some trips require a deadline for reservations and the sponsor needs a head count.