They don't have a better product, not for a long time, but they do have a famous product, with which most of the people are familiar with, unlike the competitors. They have been matched and over-matched long ago, but since virtually nobody within 99% accuracy makes research on current search engine market before typing into the box, that doesn't matter - people know google, so people go to google, however inferior their product would be. If it's not literally useless, they'll keep using it for a while now.