What Do Third-Party Candidates Really Want?

I fully support the ability of 3rd party candidates to run for office. In fact, I think expanding beyond the two-party structure could secure democracy, increase policy dialogue, and maybe even help with the polarization we see in 21st-century politics. However, and this is a big however, and I question the seriousness and commitment of many of these candidates.

See...3rd party candidates usually only show up for big elections like state house seats and the biggest in the land...president. Why are these candidates not running for school board, city council, county council, and other critical races in large numbers? I only see their names on the ballot during major election years and only for "big" seats. And I am especially critical of those running for president who have not done the work in "off" election years to build support for their causes and their base.