The Tax Question. The Drug Question. A wasted vote is voting for someone who says one thing and does another. If you want a smaller government and lower taxes, you certainly won't get either by voting Democrat or Republican. Secondly, ballot access requirements are designed to keep third parties out of politics.
Voting can help third parties' ballot access in future elections.
Otherwise, without ensured ballot access, Libertarians are subject to strict ballot access requirements that suck up our time, money, and energies. Lastly, the swing vote forces the dominant parties to listen to, and conform to, our beliefs. It's a way of voicing your opinion that you're entirely fed up with both Democrats and Republicans. On a personal level, I don't give up for the main reason that actions speak louder than words. Within my lifetime, my rights have been repeatedly chipped away at again and again.