One reason many young people give for not voting is that politicians don't care about them. This is probably a true statement. Politicians are known to care about money, hence the issue of campaign finance reform. Without money there's no campaign. A campaign is useless if there's nobody voting, so they also care about large groups of voters.
Young people compose a large part of the population.
If they were to vote in higher numbers, politicians might start caring about them. It should actually be a driving factor for young people to vote. If young people could get politicians to care about them, young people could use this power to influence politicians to act in their interests. As it is now, this country isn't operating as a democracy. The people don't hold the power.