Benefits given only to those who contribute to a collective effort, or penalties imposed only on those who do not, used to overcome free-riding in large groups.
In more detail
Mancur Olson (1965) argued that large groups cannot rely on members' shared interest in a collective good, because each can enjoy it without contributing. Organisations that succeed therefore offer private benefits to members (insurance, publications, discounts, legal services, social status) or impose sanctions on non-members (closed-shop rules, fines, exclusion). Critics note that providing selective incentives is itself a collective task, and that moral, expressive and social motives also drive participation.