Quote from Madison:
greater voter involvement, generally, would require more participation by politicians, especially those already in office. 25% voter turnout packaged into familiar, easily-manipulated groups (AARP, unions, etc.) means less physical campaigning, traveling, fewer variables, more reliance on PR agencies and ads and less of the dangers of debating and articulating positions.
and more educated voters might be less likely to forgive the scandals and negligence that feed on voter apathy, from budgetary and tax abuses to blatantly corporate-friendly laws to pre-scripted presidential 'press conferences' in lieu of a real Congressional debate on war.
sure, these things would occur with any voters, but greater involvement just means more headaches, so why make things more complicated for those in office, if you don't have to... jmho