Why Didn't The White House Use WordPress?

HealthCare.gov is "a disaster," "a failure" and "excruciatingly embarrassing" for the Obama administration.

Why didn't they just use WordPress?

Of the 14 states running their own health insurance marketplaces, five — Massachusetts, Rhode Island, Maryland, Colorado and Hawaii — decided to use WordPress to power their sites. Other markets, such as Illinois, which selected a federal partnership option, also tapped WordPress. Well these sites are far from perfect, they've performed much better than HealthCare.gov.

It didn't have to be WordPress. It could have been Drupal, Joomla, or any other open-source tool. The question is: Why did the White House feel the need to invent their website from scratch?