From Andrew Lintott's The Constitution of the Roman Republic:

The chief function of the Consuls, and an important function of the Praetors, was that of being military leaders. The authority of the Senate was most clearly demonstrated when it acted as a forum for the discussion of foreign and military policy. ... Rome's military needs determined the shape of the political year.

The magistrates with imperium did have a role in domestic matters but Rome was a martial state with its political system ordered to the requirements of an expansive military policy.