There are many different roles that you can fill. For example, next competition season I will try to become a CSA (Control Systems Advisor). They help teams troubleshoot various issues during competitions and even during matches. The role requires excellent problem-solving and communication skills.
As my description suggests, roles are well-defined, as are the relationships between them. This structure neatly avoids most of the messiness about unclear decision-making hierarchies that can be found in some other volunteer organizations. It also avoids something that really annoys me about some other volunteering opportunities, which is an unclear path of advancement to "the good roles". Of course, advancement isn't required at all and I'd guess most people don't think about it; it's just something I care about.