In a lot of crafts, yes. On the railroad the chairmen, treasurers, and stewards are all active operating engineers/conductors. You’d be hard-pressed to understand what in the hell this work occurs and what discipline access to it means unless you are currently working in a position.
At UPS, I’ll let you guys decide, but I believe that because of the extremely large amount of company grievances and employees, there comes a need for “union delegates“ for people who may have done the job previously, been fired even, but now work solely for the members. Keyword “for“