Why Aren't More Catholics "Disappointed" With Bill Bennett?

Generally because we aren't Protestant.

[T]he U.S. Catholic bishops' conference, which has pronounced on virtually every major social problem over the past few decades, has never addressed [legalized gambling] - though individual bishops and groups of bishops have sometimes opposed legalized gambling in their cities and states.

By contrast, both liberal and conservative Protestant church officials have issued repeated denunciations of legalized gambling.

They agree that it's a serious social problem and a sinful practice that builds upon greed and deceit, destroys families, exploits the poor and fosters crime.
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The catechism of the Catholic Church says wagers "are not in themselves contrary to justice" but "become morally unacceptable" if they deprive people of basic needs.

"The passion for gambling risks becoming an enslavement," the catechism warns.