It is a fact that the majority of Americans that are eligible to vote don't exercise that right. When you think of our history as a country; the deaths and personal sacrifices so many went through so that future generations could vote you should be shocked and amazed. It is not like these struggles were 500 years ago. For most of us these struggles were only in the last 30-100 years. We see people around the world fight and die for these same rights that we as society have just thrown away.
I have heard many reasons but they all boil down mostly to three categories:
People don't believe that the government is what we believe it is, the conspiracy theorists.
People live in a fantasy world of wishes when it comes to politics.
People simply do not care.