Now NIST has a new mechanical sniffer that does not need to be fed, picked up after or rewarded with a treat or playing ball. See Can a High-Tech Sniffer Help Keep Us Safe?
The issue is that dogs (normally?) don't do multiple substances. Thus you have a bomb dog, a drug dog and a cadaver dog. There isn't a Drug-Bomb-Cadaver Doodle Dog--yet!!
Dogs need a union to project their jobs! Just like those store cashiers in Oregon, dogs need a union to protect their rights to keep their jobs!