This is anecdotal, but I think the common perception is that voting just doesn't matter - politicians make promises to get votes and don't follow through after the elections. And it's the same politicians cycling in and out, year after year. Clearly people are voting for them, but just as clearly there is a large portion of the population that feels like their concerns aren't being addressed.
What's interesting is that the people I know personally who've more or less given up on politics can't be clearly identified as belonging to a specific demographic. Some of them are students, some are male knowledge workers in their 20's and 30's, some are female medical professionals and administrators in their 50's and 60's. My father, who is an academic, has the most faith in the political process among the people I know.
