To be fair...
Reporters and other broadcasters are trained from day one to fear "dead air." I suspect that many of them unconsciously relegate Mission Control to "background noise," and try to fill the space.
Also, you have to admit that Mission Control's voice appears largely at random, and a broadcaster would go nuts trying to interrupt himself every time they started talking.
That being said, starting a new conversation WHILE Mission Control is talking doesn't really have much of an excuse.
NASA TV: the way to go.