For the most part, people simply don't care. Both parties just want your money and will do whatever they want regardless of public opinion. Or so it is believed. Perhaps that is going a little overboard. Not everyone from my generation is quite that uninformed.
Some people really do care, but feel that there is no possible way to make a difference.
When one votes, they aren't even voting for the President. They are voting for a person who promises to vote for the president - the elector. However, the elector is not bound in any way to vote for who they say they will. True, while the cases where the elector has voted against his or her party are few and far between, the possibility remains. Your vote could have absolutely no effect on the election outcome.