Speaking as someone prosecuting a guy on his fifth drug charge (most of the others involve dealing) and said drugs were only found up the guy's butt when he was arrested on suspicion of other charges and searched, I was and am REAL happy about this decision.
That, and what Lief said. Metal detectors are expensive, and don't detect plastic weapons or drugs.
As a prosecutor, is there anything that diminishes the rights of the accused you would not be happy with?
I can think of certain extreme scenarios where diminishing the rights of the accused would be a negative for prosecutors.