In the U.S., why isn't turnout and activism proportional to influence?

You would expect that elections which affect people more have greater participation rates and command more attention, relatively speaking, to the people they affect. However, city council elections, state governor elections, Congress races, and Senate runoffs tend to have lower turnout than the general election.

We've been drilled for years about the importance of local elections and their influence being greater than that of federal ones, so what explains this? Let me know if I need to provide any sources to prevent this question from being closed.