In a two-party, majority rule system, moving toward the center is not likely to alienate the voters on the ends because they feel there is not another viable candidate to vote for instead. This means, there really isn’t any penalty for a candidate chooses to move toward the middle. And it explains why all politicians end up sounding the same.
Too cynical? Try reading this excellent primer on public choice theory.
But what can you do about it? Join a political party. They are small enough now that you can make a real difference to the local centre ground of debate. Join Wycombe Conservatives here.