Voting is the act by which an individual expresses support or preference for a certain motion, proposed, candidate, or selection of candidates for a vote, in secret or public. It is, therefore, a method of decision making in which a group, such as a board or an electorate, tries to measure their joint opinion (Wilensky, pp. 621). Rightly or wrongly, voter turnout in an election is viewed by many as some sort of measure of the health of a nation's (or province's) democracy. And because voter turnout is on the decline, this is seen by many as a sign that the democracy is in bad shape.
Discussion
It is not that the Turnout Nerds have some vast constituency of voters who share their concern. Voter turnout is the kind of imaginary issue that spurs people to parrot pieties to pollsters, but the turnout itself is a perfect revealed-preference measure of how much people actually care. Aside from a few unfortunates who slip and fall or get hit by buses on their way to the polls, there can be almost no such thing as a person who is really concerned about turnout, but who stays home on Election Day. Everyone have near-total control over whether they turn out or not. The cost of going to the polls is pretty much zero. So the issue, if there is an issue, must be that a lot of people think that voting isn't even worth the zero, that they personally accomplish nothing or less than nothing by voting: not even the reinforcement of a useful social norm or the cultivation of a private sense of satisfaction (Teixeira, pp. 51). Some of them are surely right about this.
If voter turnout really does concern you, you will make every effort to go vote if only to ensure that you don't contribute to the problem. It can also be right when people argue that the issue isn't voter turnout (or lack thereof) but that more and more people don't believe that there is any value in voting.
However, if more and more people believe that there is nothing to be gained by voting, that voting has no value at all, and then more and more people will not vote, and voter turnout will continue to decline. Like it or not, this will become problematic. It is true, again, that it is mostly the “Voter Turnout Nerds” ...