Why do interest groups focus more on prime ministers and cabinets in parliamentary systems?

In parliamentary systems, interest groups focus their lobbying efforts on the prime minister and the cabinet because these bodies hold the concentration of executive and legislative power.12

Unlike presidential systems, such as that of the United States, where power is divided among branches, parliamentary systems typically draw the executive directly from the legislature. Due to strong party discipline, the government—led by the prime minister and cabinet—is generally able to ensure that its legislative agenda is enacted without significant opposition from the parliament.1234

Because the executive branch initiates legislation and controls the policy-making process, interest groups find that the most effective way to achieve favorable policy outcomes is to engage directly with the decision-makers in the cabinet rather than focusing on individual legislators. Consequently, the legislative branch in these systems is often less critical for lobbying than the executive, as the latter effectively monopolizes the power to drive the government's agenda.12