It was a great idea, it worked, it brought in a wave of new fresh faces and swept out stale useless Reps.
Used once and discarded, I don’t know why
What made it so effective was that it was relatively benign — which meant it was pretty easy to adopt most of the measures once the GOP won control of Congress. In fact, it was even pathetic that some of the provisions of the Contract hadn’t already been in place as a matter of fact (requiring Congress to abide by all laws that apply to the rest of the country, for example).