Final answer:
The expansion of public-interest lobbies in the 1960s can be attributed to the enlargement of governmental responsibilities. As the government's role in society increased, people and organizations mobilized to influence policy through sophisticated lobbying efforts.
Step-by-step explanation:
The growth of numerous public-interest lobbies in the 1960s was largely a result of the enlargement of governmental responsibilities. During this period, the United States saw increased governmental involvement in various aspects of society and the economy. As the government became more deeply entwined with these areas, people with common interests began to organize in order to solicit government support for their concerns.
Interest groups arise from a complex mix of factors, including societal shifts, technological advancements, and reaction to specific events or policies. For instance, some interest groups are formed in direct response to particular governmental actions or court decisions, such as the National Right to Life Committee after Roe v. Wade.
Lobbying efforts by these groups have become more sophisticated over the years, often involving professional lobbying firms that seek to influence government policy on behalf of their clients, which may include businesses, public interest groups, or other organizations.