Why is pre-school education so popular?

"The welfare state is relatively good at giving people money: you collect the taxes, write a check, and now people have money. The welfare state has proven very bad at giving people stable jobs and stable families, a vibrant community life, promising career tracks, or a cure for their drug addiction. No wonder so many hopes now seem to be pinned on early childhood education, far in excess of the evidence to support them: it is the only thing we have not already tried and failed at." From an interesting piece by Megan McArdle here.