Librarianship is a profession.
Librarians profess the field and share a belief in a joint ownership and responsibility for it.
It is true that some people are in a better position to volunteer time than others, and that some can better afford to pay for a hotel and go to conferences, but it is not just people with funding who do so, and not just administrators or people from large libraries who contribute to the work of the profession. It includes students, research library directors, and everyone in between. Every member makes a personal choice about whether volunteering for committee work is possible or worthwhile to them, or whether they feel personal obligation to spend time and money on it. It also may be possible to contact a committee chair and ask whether there is some way that a non-member can be of assistance. People without previous appointments and people from various types of libraries and related organizations get appointed all the time.