Most workers assess their union on the basis of the performance of their shop stewards.
When stewards are fair and efficient, members feel that the union is fair and efficient. Likewise, if stewards express enthusiasm for projects, members will take interest as well. When they succeed in making sure the collective agreement is upheld, members respect them.
In the minds of members, stewards are their voice within the union structure and represent the union itself.
The steward must, among other duties, protect the rights of the workers, see to the implementation of the collective agreement, strengthen union positions and win the support of members.