Because the Net won't have any effect on real world demographics. In terms of reaching out and touching your representative, you can already do that via snail mail and the phone. Your opinion and your vote carry exactly as much or as little weight as it always has, no matter how you deliver it. Speaking of your vote. But polling is just 'acclamatory democracy,' a degenerate case of democracy.
True democracy involves discussion and deliberation and is slow by definition.
It requires debate, not just clicking on For or Against buttons. Furthermore, it requires opportunities for citizens to influence important issues. Instead, the Information Highway will give us more opportunities to vote on issues such as whether or not the First Spouse should dye his or her hair. Instead of democracy, we'll get Oprahcracy. That may be overstating the case, but even if instant elections are conducted on the Net on the more hardcore stuff, on referendums, candidates, etc., as we can tell by the polls already being taken daily, instantaneousness does not serve the democratic process.