Why did smugglers in Pakistan tried to hide heroin inside hollowed-out onions?

Criminals in Pakistan have been caught allegedly trying to smuggle heroin inside hollowed-out onions in an attempt to thwart sniffer dogs, it’s been reported.
    Security forces in Karachi uncovered the plot when they raided a home in the city and seized 61.5kg of "high quality" drugs, which they valued at ￡250,000. Five suspects were arrested.
    According to the country’s Anti-Narcotics Force who carried out the operation, the gang were hollowing out onions, inserting capsules of heroin, then capping the onions with glue. The smugglers confessed that the smell of the onions would hopefully prevent sniffer dogs from detecting the drugs. In the end, the gang were apprehended following a surveillance operation.