What are some reasons the United States has low voter turnout?

Voter turnout in the United States is a complex situation, but some possible reasons for the low turnout are required registration, the disenfranchisement of felons, and the fact that voting is voluntary instead of mandatory. Other sources cite the two-party system and the formality of the electoral college as reasons.

David Koyzis argues that people are over-saturated with opportunities to vote, so because there are multiple voting opportunities, such as in primaries, local elections and national elections, every few years as opposed to once every four or five years, people take voting opportunities less seriously and thus tend to vote less frequently.