I could go on and on, but I think you understand my point of view. When you serve on the curriculum committee they get your input as to where the library can fit into their curriculum - not as a babysitter for their free period but as a part of the teaching team. You get the benefit of their expertise and a better understanding of what they intend and are required to teach. This enables you to select material for the library and classroom that complement what they are trying to do. That's how resource-based learning works best.
Leadership takes several forms.
I don't think LMS have to be subject matter experts. We have LMS on all curriculum teams. One of the strengths they have is that they are the one person who has an overview of the entire subject. They know what teachers teach at different grade levels. Being able to share that is a type of leadership.