The election is merely the hiring process. Getting elect is necessary, but not where the job ends. It is post-election when the constituents start hammering you with their demands and as their representative you have to find the general sentiment of the crowd.

It is true that not everyone believes in the democratic process and, as such, will never speak to their representative again, if they even managed to during the election campaign, but then they're not really constituents in any meaningful sense and can be safely ignored.