Also some people are terrified of dogs so having one sniff over them would be worse than being groped. Not that the TSA cares about feelings or anything though.
Thats why airport sniffer dogs are often beagles rather than the German Sheppard/Bloodhounds used for cargo.
Beagles are small cute and non-threatening, and they don't have to climb all over you to smell explosives.
By contrast the police here got German Sheppards to sniff for drugs on suspects on the street. It turns out the police didn't actually buy trained sniffer dogs - they just wanted something big and fierce looking to 'encourage' people to cooperate.
